You're listening to the Global News Podcast from the BBC World Service.

Hello, I'm Oliver Conway. This edition is published in the early hours of Friday the 2nd of May.

President Trump replaces his national security adviser, Mike Waltz.

Ukraine hails the minerals deal with the US as a truly equal partnership.

And we look ahead to the Australian election this weekend.

Also in the podcast, a world first for Alzheimer's research.

We sprint into a taxi, into our lab,

and try and really get it from brain into the incubator in less than two hours.

We hear from a scientist using live brain tissue in the hunt for a cure for dementia.

In the week, he marked 100 days of his second presidency. Donald Trump has carried out his first

cabinet-level sacking. The US president confirmed he was replacing Mike Walz as national security adviser.

In theory, Mr. Walts is being moved to the post of UN ambassador,

but he'll need to be confirmed by the US Senate.

And that may prove tricky, given Mr. Walts' key role in Signal Gates

when he mistakenly added a journalist to a White House group chat

about an attack on the Houthis in Yemen.

The U.S. Secretary of State Marco Rubio will now double up as National Security Advisor on an interim basis.

News which surprised State Department spokesperson Tammy Bruce as she heard about it during a briefing.

So that is the miracle of modern technology and the social media. So that is an exciting moment here.

I think that, as I know, Secretary Rubio, this is a man who, as I think you all know,

has worn several hats in managing the nature of what's happened here at the

State Department at USAID. He's someone who's well known by the president.

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