Katherine Donohue Papillon
United States Agency for International Development, 2023 fellow
Katherine Donohue Papillon serves as the Deputy Director for the U.S. Agency for International Development’s Office of Transition Initiatives (OTI) in the Bureau for Conflict Prevention and Stabilization.
Sean Peters
Nuclear Regulatory Commission, 2023 fellow
Sean E. Peters is an accomplished leader from the U.S. Nuclear Regulatory Commission (NRC).
Christopher O’Connell
Department of Health and Human Services, 2023 fellow
Christopher O’Connell is a public health leader who builds teams to innovate and thrive through change.
Maria E. Temiquel
Department of Labor, 2023 fellow
Maria E. Temiquel has been serving, protecting, and advancing education and employment goals throughout her federal career. Ms. Temiquel brings extensive experience in strategic development and implementation, building a progressive performance management culture.
Lyne-Robert Desroches
Department of Homeland Security, 2023 fellow
Ms. Desroches is an attorney and dedicated public servant who has been practicing immigration law in the nonprofit and private sector since 2013.
Vanessa Sloane
Internal Revenue Service, 2023 fellow
Vanessa Sloane has more than 27 years of Federal Government experience in the Internal Revenue Service (IRS) and currently serves as Executive Assistant to the National Taxpayer Advocate (NTA) in the Taxpayer Advocate Service (TAS), an independent organization within the IRS.
Carmen Coles Tull
United States Agency for International Development, 2023 fellow
Carmen Coles Tull is a public policy strategist, coalition builder, and advocate who is committed to addressing the world’s most significant global health challenges.
Marc Tkach
Millennium Challenge Corporation, 2023 fellow
Marc Tkach, founder of the Millennium Challenge Corporation, is a global infrastructure specialist, project management coach, and change agent.
Aditi Sehgal Shah
Department of State, 2023 fellow
For more than fifteen years, Aditi Sehgal Shah has worked with multiple federal agencies as a labor and employment litigation attorney, working on a variety of personnel issues from transgender discrimination to the COVID-19 pandemic.
Mindy A. Kaiden
Department of Transportation, 2023 fellow
Mindy Kaiden is the Assistant Chief Counsel for Operations and Administration at the Federal Highway Administration (FHWA ) in the Department of Transportation.
Dr. Patrick Clowney
Department of Education, 2023 fellow
Dr. Patrick Clowney is a combat veteran of the Global War on Terrorism. He has risen up the ranks in the U.S. Air Force, private sector, and the Federal Government.
Dominic Beamer
U.S. Census Bureau, 2023 fellow
Dominic Beamer is an empathetic leader and collaborator dedicated to elevating government initiatives and solving the complex problems they face.
Ashlie B. Flegel
National Aeronautics and Space Administration, 2023 fellow
Ashlie Flegel is an engineer and project manager who has made significant impacts to aviation research focusing on developing partnerships, building teams, and establishing a strategic vision.
Diana Rutberg
National Institute of Health, 2023 fellow
Diana Rutberg has been the Chief Grants Management Officer for the National Institutes of Dental and Craniofacial Research since 2013. In this role, Ms. Rutberg oversees the business operations for a diverse portfolio of 1,000 research grants totaling more than $400 million.
Brian Mohr
Department of Agriculture, 2023 fellow
Brian Mohr is a servant leader and Veteran Marine with a successful history leading projects and people in the military, private, and federal sectors.
Michael Boyce
United States Citizenship and Immigration Services, 2023 fellow
Michael Boyce is Chief of the Innovation and Design for Enhanced Adjudication (IDEA) Division at the United States Citizenship and Immigration Services’ (USCIS) Refugee, Asylum and International Operations (RAIO) Directorate, where he oversees technology, analytics, and innovation for USCIS’ humanitarian immigration programs.
Anny Pachner
Department of the Treasury, 2023 fellow
Anny Pachner is a senior leader and communications strategist with a history of driving transformational change in the public and private sector.
Dr. Christopher P. R. Hoppel
Department of Defense, 2023 fellow
Dr. Christopher P. R. Hoppel is an accomplished engineer and program manager who leads innovative research to solve complex technical problems.
Anil Chaudhry
General Services Administration, 2023 fellow
Anil Chaudhry has more than 20 years of progressive leadership experience in technology delivery, operations, and program management in the defense, intelligence, and national security sectors.
Dr. Michelle Hawkins
Department of Commerce, 2022 fellow
Motivated leader and accomplished scientist with expertise in weather and climate policy.
Kylie Gaskins
Department of Commerce, 2022 fellow
Chemical engineer, innovative process improver, and employee engagement enthusiast.
Eraina R. McCoy
Department of Housing and Urban Development, 2022 fellow
Servant leader delivering impactful results through developing highly effective teams.
Nichelle Johnson Billips
United States Agency for International Development, 2022 fellow
Experienced, innovative leader and international legal expert.
Adam C. Kavalsky
Social Security Administration, 2022 fellow
Accomplished leader who collaborates to solve problems in both an office and a field environment.
Bich-Thuy Sim
Department of Defense, 2022 fellow
Physician and thought leader in healthcare policy and innovation.
Carlton Drew
Department of Health and Human Services, 2022 fellow
Government leader focused on outcome measures and change management.
Patricia Pless
Department of Homeland Security, 2022 fellow
A public sector servant supporting U.S. Customs and Border Protection in strategic planning and driving efficient outcomes for the mission directive.
Lea-Ann Bigelow
Office Federal Financial Management, Transparency and Grants, 2022 fellow
Solutions-driven leader with a passion for continuous improvement in operations and service delivery.
Osasu Dorsey
Department of Defense, 2022 fellow
Trusted senior policy adviser, attorney, and collaborative leader.
Pam Sessoms
Department of Health and Human Services, 2022 fellow
Strategic thinker, resilient, conflict manager, coalition builder, executive coach, and mentor.
Frances Chang
Department of Justice, 2022 fellow
International law expert and cross-agency, cross-cultural collaborator aiding the Department of Justice in foreign engagement.
Eric S. Coleman
Department of Agriculture, 2022 fellow
Veterinarian, agriculture, and public health professional who collaborates globally to bolster national security, advance foreign policy objectives, and strengthen emergency response preparedness.
Damiana Astudillo
Millennium Challenge Corporation, 2022 fellow
International Development Leader in Agriculture, Rural Development, Public Policy, and Social and Gender Inclusion.
Tim Hoyt
Department of Defense, 2022 fellow
Military Clinical Psychologist and data-driven decision maker striving to reduce mental health stigma and support service member transitions.
La Tonya Mimms
Department of Transportation, 2022 fellow
A seasoned policy writer, with experience in developing and implementing national mission critical programs.
Barbara Sanford
Nuclear Regulatory Commission, 2022 fellow
A valued civil servant with a proven leadership record in government employing innovative workforce development tactics to adapt during the COVID-19 pandemic.
Lucinda A. Wade
Department of State, 2022 fellow
IT executive whose expertise and collaborative skills advance the U.S. State Department’s organizational mission.
Albert (Al) Herrera
Department of Labor, 2022 fellow
Federal leader in complex program, budget, and policy innovation and implementation.
Laura A. Sepulveda Ramirez
Department of Transportation, 2022 fellow
Human Resources leader, workforce strategist, and diversity, equity, and inclusion champion.
Jay Snipes
Department of the Treasury, Centralized Receivables Service, 2022 fellow
Senior leader recognized for sustained excellence in operational and portfolio project management with a strong commitment to service in organizations and the community.
Dr. Brian Holm-Hansen
Department of Defense, 2021 fellow
Mechanical engineer and leader in aviation research.
Jacob Parcell
General Services Administration, 2021 fellow
Public servant dedicated to customer service and innovative design.
Christine Assili
Department of Homeland Security, 2021 fellow
Federal leader in strategic communications and transportation security.
Katherine Tyner, PhD
Department of Health and Human Services, 2021 fellow
Expert in complex drug formulations and science policy.
Melinda Campos
United States Agency for International Development, 2021 fellow
Experienced leader, attorney, and expert in international law.
John D. Tuminaro
Department of State, 2021 fellow
Seasoned diplomat and food security advisor.
William J. Weinig
Department of Defense, 2021 fellow
Government leader with broad experience managing teams in acquisition environments.
Terry O. Woods, Ph.D.
Department of Health and Human Services, 2021 fellow
Innovator focused on providing patients access to safe, effective medical devices.
David M. Gratz
Department of Veterans Affairs, 2021 fellow
Supervising attorney with expertise in veterans’ law.
Victor Hall
Nuclear Regulatory Commission, 2021 fellow
Focused on the safe use of nuclear power technology.
Scott Jackson
Department of Defense, 2021 fellow
Public servant focused on building better government.
Shantá M. Cardiel
General Services Administration, 2021 fellow
Leader in federal workspace management.
Ariel Novick
Department of Health and Human Services, 2021 fellow
Federal leader in healthcare program innovation & implementation.
Candice Gayton Spalding
Department of Labor, 2021 fellow
Executive leader in federal administrative services.
Reena Duseja
Department of Health and Human Services, 2021 fellow
Physician and policy researcher for cross-cutting solutions.
Thomas Tso
Department of Labor, 2021 fellow
Expert on retirement and welfare benefits law.
Mary Eisenhauer
Department of Defense, 2021 fellow
Resource-focused, results-oriented federal executive.
Heather M. Shirey
Department of Defense, 2021 fellow
Innovative engineer, scientist, and technical advisor who collaborates globally to solve problems.
Christopher G. Moore
Department of Transportation, 2021 fellow
Dedicated public servant and responsible citizen.
Bronson Armstrong
Department of Defense, 2020 fellow
Bronson Armstrong is an accomplished national security and business expert. He is an enterprise-focused, results-oriented federal executive with experience leading teams at all levels with a strategic focus.
Sharice Smith-Lewis
Department of Veterans Affairs, 2020 fellow
Sharice Smith-Lewis joins us from the Veterans Health Administration (VHA), Department of Veterans Affairs (VA).
Sarah B. Smith
Department of Health and Human Services, 2020 fellow
Sarah Smith joined the White House Leadership Development Program from the U.S. Centers for Disease Control and Prevention (CDC).
Lance Kvetko
Department of Justice, 2020 fellow
Lance Kvetko is the Chief of Laboratory Management and Operations for the Drug Enforcement Administration (DEA).
Maria Cheeks
Department of the Treasury, 2020 fellow
Maria Cheeks is an innovative and results-oriented public servant with over 28 years in tax administration and policy implementation at the Internal Revenue Service (IRS).
Anthony Garza
Department of Health and Human Services, 2020 fellow
CAPT Garza serves as the Senior Program Manager in the Office of Counterterrorism and Emerging Threats (OCET) at the US Food and Drug Administration (FDA).
Anna Ramachandran
Department of the Treasury, 2020 fellow
Anna Ramachandran is a dedicated public servant with extensive experience in leading multi-million Information Technology projects and programs for over 20 years.
Tracy Hancock
Department of Agriculture, 2020 fellow
Tracy is the Director of Knowledge Management and Communications (KMC) in USDA Forest Service with Research & Development.
CAPT Cheryl A. Ford, DR.P.H.
Department of Health and Human Services, 2020 fellow
CAPT Cheryl A. Ford is a Health Services Officer in the U.S. Public Health Service Commissioned Corps.
Houman Rasouli
Nuclear Regulatory Commission, 2020 fellow
Houman Rasouli is a results-driven executive with more than 25 years of leading private and public organizations to build agile, high functioning, and trusting environments, where everyone can thrive and achieve their full potential.
Denis A. Ortega, ED.D.
Department of Transportation, 2020 fellow
Denis Ortega is an organizational effectiveness and human resources expert specializing in enhancing the effectiveness of teams, leadership development, and coaching.
Paul Spanos
Department of Labor, 2020 fellow
Paul Spanos is a senior trial attorney with the U.S. Department of Labor, Office of the Solicitor, in Boston, Massachusetts.
Chad Clifford
Department of Homeland Security, 2020 fellow
Chad Clifford is an attorney and leader in the Department of Homeland Security - Federal Emergency Management Agency’s (FEMA) Office of Chief Counsel with over 13 years of career federal experience.
Kim Tuminaro
Department of State, 2019 fellow
Kim Tuminaro is a transformational leader who mobilizes people, ideas and networks to advance U.S. economic interests with the European Union.
Lelia Jackson
Department of Veterans Affairs, 2019 fellow
Lelia Jackson serves as the Director of the Center for Compassionate Care Innovation, where she leads VA’s efforts to explore emerging treatments and therapies to enhance Veterans’ well-being.
Kimberly Smith
United States Agency for International Development, 2019 fellow
Kimberly Smith is an expert in development finance policy and statistics which she gained during her 18-year career in international development.
Gloria J. Perry, PMP
Department of Defense, 2019 fellow
Ms. Gloria J. Perry currently serves as a Senior Advisor for the $10B Air Force Small Business Program, where she advises Senior Acquisition Leaders on acquisition strategies to provide innovative solutions to warfighter needs, ensuring affordability, competition and maximum small business participation.
Richard A. Skokowski
Nuclear Regulatory Commission, 2019 fellow
Mr. Skokowski has been a role model of the Nuclear Regulatory Commission’s (NRC) values during his distinguished 28 year career.
Bradley Jewitt
National Aeronautics and Space Administration, 2019 fellow
Bradley Jewitt is an accomplished, enterprise-focused, results-oriented federal mission support services executive with experience at all levels of government and the military.
Helena Fu
Department of Energy, 2019 fellow
Helena Fu is an environmental planner, energy policy analyst, and foreign affairs specialist with over 16 years of experience in leading and managing complex projects in the United States and overseas for the public and private sectors.
Khoa Vo
National Aeronautics and Space Administration, 2019 fellow
Khoa Vo is chief of the Spaceport Systems Branch in Exploration Research and Technology Programs at NASA’s Kennedy Space Center in Florida.
Jay Huie
General Services Administration, 2019 fellow
Jay Huie joined the White House Leadership Development Program to explore and explain the government’s ability to use information and information technology to deliver visibly better results, improve insight and accountability, and unlock the economic potential of federal data.
Tamara S. Hamaty
Department of Health and Human Services, 2019 fellow
Tamara S. Hamaty serves as Associate Director for Public Health Intelligence for Centers for Disease Control and Prevention (CDC)/Department of Health and Human Services.
Salim R. Mawani, CPA, CGFM
Department of Transportation, 2019 fellow
Salim Mawani is a member of Department of Transportation's (DOT) Federal Motor Carrier Safety Administration (FMCSA).
Robert Hankinson
Department of State, 2019 fellow
Robert Hankinson is a cybersecurity expert, currently serving as the Information Integrity Branch (IIB) Chief at the U.S. Department of State (DOS).
Anselm Beach
Department of Homeland Security, 2019 fellow
Anselm Beach is a combat veteran of Operation Desert Storm. He is dedicated to excellence in public service and has held positions of increasing responsibility in the U.S. Army, and the Federal Government.
Clifford McCoy
Transportation Security Administration, 2019 fellow
Cliff McCoy serves as Deputy Chief Security Officer (DCSO) for the Transportation Security Administration (TSA) and is assigned to the Law Enforcement and Federal Air Marshal Service.
Dr. Michelle Dorsey
Department of Veterans Affairs, 2019 fellow
Dr. Michelle Dorsey is a dedicated public servant, committed to driving excellence and innovation in health care.
Yaro T. Kulchyckyj
Department of State, 2019 fellow
Mr. Yaro T. Kulchyckyj is a highly innovative and results-oriented professional public servant, committed to excellence in government, integrity in character, and efficiency in performance.
Nicoletta Giordani
Office of Management and Budget, 2019 fellow
Nicoletta S. Giordani is a national security and business expert specializing in corporate strategy, mergers and acquisitions, national security investment reviews, and Federal budget formulation and execution.
Jeannette Mandycz Connor
Social Security Administration, 2019 fellow
Jeannette Mandycz Connor began her career with Teach for America, as a teacher and new teacher trainer in Atlanta, Houston, and New York City.
Bryan Swann
Department of Treasury, 2018 fellow
Bryan is a public servant, and public speaker/entrepreneur originally from Maryland.
Paul Wagner
Army Corps of Engineers, 2018 fellow
Currently a Division Chief at the U.S. Army Corps of Engineers Institute for Water Resources (IWR), where I serve as a senior ecologist and supervisor to 16 subject matter experts working on water resources science, policy, and planning methods.
Nathan Sanfilippo
Nuclear Regulatory Commission, 2018 fellow
Nathan is an expert in nuclear regulatory policy, licensing, and oversight, which he has developed over his 15 year career at the U.S. Nuclear Regulatory Commission (NRC).
Talin Zarookian
Department of Homeland Security, 2018 fellow
Talin Zarookian serves as the Section Chief for Resource and Program Management for the National Explosives Detection Canine Team Program within the Transportation Security Administration’s Office of Security Operations.
Jennifer K. McDannell
Department of Justice, 2018 fellow
Jennifer K. McDannell is a Deputy Chief at the United States Department of Justice, Civil Rights Division, Disability Rights Section.
Michael Dunlevy
Defense Nuclear Facilities Safety Board, 2018 fellow
Michael is a nuclear-chemical engineer currently serving as the Lead Engineer for nuclear safety oversight activities at the Los Alamos National Laboratory (LANL) for the Defense Nuclear Facilities Safety Board (DNFSB).
Victoria Premaza
Department of Energy, 2018 fellow
Victoria has over fifteen years of domestic and international engineering and project and program management experience.
Leticia Sierra
Department of Labor, 2018 fellow
Leticia Sierra is a senior attorney specializing in immigration in the U.S. Department of Labor, Office of the Solicitor.
Kyra Stewart
Department of Transportation, 2018 fellow
Kyra M. Stewart serves as the Director of Innovation at the US Department of Transportation.
Matthew Lunder
Department of Justice, 2018 fellow
Matthew Lunder serves as a trial attorney at the United States Department of Justice in the Antitrust Division’s Criminal Enforcement Program.
Jerri Marr
Department of Agriculture, 2018 fellow
Jerri is the Assistant Director for Recreation, Heritage and Volunteer Resources (RHVR) for the USDA Forest Service in Washington D.C.
Scott Kelberg
Department of Homeland Security, 2018 fellow
Scott is the Assistant Director for the National Training and Education Division (NTED), National Preparedness Directorate, FEMA.
Cheryl L. Mcdonald, M.D.
Department of Health and Human Services, 2018 fellow
Dr. McDonald is a Medical Officer at the National Institutes of Health (NIH).
Sabrina Ferguson-Ward
Department of Agriculture, 2018 fellow
Sabrina has over 22 years of federal service. She was appointed as Director of Resource Management Programs in June 2010 for Biotechnology Regulatory Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture (USDA).
Thea Calder
PMC Fellow, 2017 fellow
Assisting with the White House Leadership Development Program, specifically, coordinating the alumni group.
Kelly Alexander
Department of Defense, 2017 fellow
Kelly. Alexander serves as the ASA(ALT) Director, COE for System of Systems Engineering & Integration (SoSEI) to oversee, direct and guide the Army’s transition to COE that will enable the Army’s Mission command Network 2020.
Eileen Vidrine
Department of Defense, 2017 fellow
Eileen Vidrine joined the Office of the Under Secretary of Defense for Intelligence in 2012, as the DoD Intelligence Community Enterprise Architect for the Human Capital Management Office (HCMO).
Kathleen Carson
General Services Administration, 2017 fellow
Kathleen Carson currently serves as the Director of the U.S. General Services Administration (GSA), Federal Acquisition Service’s (FAS) Office of Customer Accounts & Research, Customer Outreach Division.
Noreen Hecmanczuk
Department of Labor, 2017 fellow
Noreen M. Hecmanczuk is the Director of the Office of Succession Planning and Employee Engagement at the U.S. Department of Labor’s Mine Safety and Health Administration.
Bernadette Adams
Department of Education, 2017 fellow
Bernadette Adams is a recognized leader in educational technology policy.
Vicki Simons
Environmental Protection Agency, 2017 fellow
Vicki Anderson Simons is a Senior Advisor in the Office of Water at the US Environmental Protection Agency.
Kenneth Wright
National Aeronautics and Space Administration, 2017 fellow
Mr. Kenneth Wright is the Chief Operating Officer of the Research Directorate (RD) at NASA Langley Research.
Emily Kilcrease
Department of Commerce, 2017 fellow
Emily Kilcrease is an international trade and investment expert, specializing in national security investment reviews, trade agreement negotiation and compliance, and trade capacity building.
Dr. David Armitage
Department of State, 2017 fellow
Dr. David Armitage heads the European Regional Analysis unit at the U.S. Department of State’s Bureau of Intelligence and Research (INR).
Robert Green
General Services Administration, 2017 fellow
Robert Green is currently the director of the GSA Region 5, Design and Construction division overseeing a design and construction program of approximately $575 million in capital construction projects.
Kevin Mcghaw
National Aeronautics and Space Administration, 2017 fellow
Kevin McGhaw is an expert in the fields of strategic communications and external affairs with over 22 years of experience in congressional relations, legislative strategy, stakeholder engagement, and public communications.
John Rigg
Department of Health and Human Services, 2017 fellow
John Rigg has worked as Director of the Office of Policy Analysis since 2012. Prior to his work at HRSA, he was a Senior Medicare Analyst at the Centers for Medicare & Medicaid Services (CMS) Office of Legislation.
Mark Ackiewicz
Department of Energy, 2017 fellow
Mark Ackiewicz is the Director for the Division of Carbon Capture and Storage (CCS) Research and Development (R&D) at the Department of Energy (DOE).
Carolyn Fleming-Williams
Federal Communications Commission, 2017 fellow
Carolyn Fleming-Williams provides leadership in advancing OCBO’s mission to promote competition and innovation in telecommunications ownership and information services.
Kala Surprenant
WHLDP Fellow, 2016 fellow
Kala Shah Surprenant is a senior attorney from the Office of the General Counsel at the U.S. Department of Education (ED).
Christopher Landers
WHLDP Fellow, 2016 fellow
Mr. Landers has worked in the field of nuclear nonproliferation for over ten years, starting with short stints supporting the United Nations Department for Disarmament Affairs and the Comprehensive Nuclear Test Ban Treaty Organization Preparatory Commission.
Claire Ehmann
WHLDP Fellow, 2016 fellow
Claire Ehmann is an expert on international development, with over twenty years of experience working on global democracy issues.
Dr. Andrew Garrett
WHLDP Fellow, 2016 fellow
Dr. Andrew Garrett, MD, MPH, is the Director of the National Disaster Medical System (NDMS) at the U.S. Department of Health and Human Services (HHS).
Elaine Ho
WHLDP Fellow, 2016 fellow
Elaine P. Ho is the Deputy Chief of Staff at the Internal Revenue Service.
Darbi Dillon
WHLDP Fellow, 2016 fellow
Darbi S. Dillon is currently serving as a Fellow in the White House Leadership Development Program.
Jeremy Pelter
WHLDP Fellow, 2016 fellow
Jeremy Pelter is currently the Business Operations Officer for the Office of Investment and Innovation at the U.S. Small Business Administration (SBA).
Tiffany Lightbourn
WHLDP Fellow, 2016 fellow
Dr. Lightbourn is the Chief of Research & Evaluation in the Office of Policy and Strategy at United States Citizenship and Immigration Services.
James Ghiloni
WHLDP Fellow, 2016 fellow
Mr. Jim Ghiloni is the Professional Services Program Management Executive within the Federal Acquisition Service (FAS) at the General Services Administration (GSA).
Daniel Schoettinger
WHLDP Fellow, 2016 fellow
Daniel Schoettinger currently serves as the Deputy Director, Office of Selective Acquisitions (OSA) within the Office of the Chief Procurement Officer (OCPO) for the Department of Homeland Security (DHS).
Jack Schreibman
WHLDP Fellow, 2016 fellow
Jack Schreibman is the Deputy Associate Administrator for Administration for the Maritime Administration, U.S. Department of Transportation (DOT).
Dr. Susan Camarena
WHLDP Fellow, 2016 fellow
Dr. Camarena leads the FTA Learning and Knowledge Management Group.
Marc Wynne
WHLDP Fellow, 2016 fellow
Marc Wynne started his federal career in 2010 joining the Centers for Medicare & Medicaid Services (CMS), Department of Health and Human Services, as a Senior Advisor assisting in the implementation of the Affordable Care Act.
Jessica Powers
WHLDP Fellow, 2016 fellow
Ms. Powers is the Director for Space Policy Engagement in the Office of the Deputy Assistant Secretary of Defense for Space Policy.
Bruce Hollywood
WHLDP Fellow, 2016 fellow
Mr. Bruce Hollywood is a member of the initial cohort of the White House Leadership Development Program.
Gordon W. Weynand
WHLDP Fellow, 2016 fellow
Gordon W. Weynand is the Director, Technical Services Division, within the Office of Afghanistan & Pakistan Affairs.