The S&P/ASX 200 Index (ASX: XJO) has started the week positively. In afternoon trade, the benchmark index is up 0.5% to 7,811.3 points.

Four ASX shares that are rising more than most today are listed below. Here's why they are climbing:

The Fortescue share price is up 3% to $25.40. This may have been driven by news that the mining giant's recently deployed electric excavator has now moved one million tonnes of material since going into action. Importantly, management advised that at times the electric excavator was performing better than its diesel equivalent.

The Gold Hydrogen share price is up 14% to $1.47. This morning, this natural hydrogen and helium exploration and development company announced strong results from its Ramsay 1 and Ramsay 2 well testing. According to the release, the test confirmed up to 17.5% purity for helium, which ranks amongst the highest purity levels globally.

The MMA Offshore share price is up 11% to $2.61. This follows news that the marine service provider has received and accepted a takeover offer. According to the release, the company has entered into a binding scheme implementation deed with Cyan MMA Holdings for the proposed acquisition of all its shares via a scheme of arrangement. The board unanimously recommends shareholders vote in favour of the $2.60 cash per share offer at the scheme meeting. Though, with its shares now trading above the offer price, it's possible that some investors believe a competing bid will materialise.

The Sims share price is up almost 3% to $12.22. This morning, analysts at UBS upgraded the scrap metal company's shares to a buy rating with an improved price target of $14.50. The broker believes that its outlook is improving and highlights the discount its shares trade at compared to book value.