In afternoon trade, the S&P/ASX 200 Index (ASX: XJO) is on form again and pushing higher. At the time of writing, the benchmark index is up 0.5% to 8,448.9 points.

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

DroneShield Ltd (ASX: DRO)

The DroneShield share price is up 7% to 77.5 cents. Investors have been buying this counterdrone technology company's shares after it announced a number of key appointments. Commenting on them, DroneShield's CEO, Oleg Vornik, said: "They are world class talent, coming at this important time as counterdrone threats are rapidly growing around the world. They will be involved in ongoing positioning of DroneShield as a pre-eminent defence technology company in Australia and globally. These appointments reflect the significant growth in our capabilities, across business development, technology, and operations."

Imricor Medical Systems Inc (ASX: IMR)

The Imricor Medical Systems share price is up 20% to $1.28. This morning, the medical device company announced a licensing agreement with Switzerland's ADIS. It is a software company that has been working with Imricor to build artificial intelligence (AI) modules to integrate into Imricor's NorthStar 3D mapping system. While not yet approved for commercial sale, regulatory processes are well progressed. As a result, the company is making preparations for planned commercial launches across Europe, the United States, and the Middle East in 2025.

Insurance Australia Group Ltd (ASX: IAG)

The IAG share price is up 3.5% to $8.47. This has been driven by news that the insurance giant has agreed to pay $855 million for 90% of RACQ's existing insurance underwriting business. It also has an option to acquire the remaining 10% in two years on consistent terms. As part of the agreement, the two parties will enter a 25-year exclusive strategic alliance to provide RACQ general insurance products and services for RACQ members and Queenslanders. The transaction will be funded from surplus capital and is expected to be earnings per share accretive in the first full year of ownership.

Sayona Mining Ltd (ASX: SYA)

The Sayona Mining share price is up 3% to 3.3 cents. This follows the release of the lithium miner's annual general meeting presentation. At the event, the company's chair spoke about its proposed merger with Piedmont Lithium (ASX: PLL). He said: "This transaction establishes a North American lithium leader with unrivalled project optionality and a robust pipeline of growth projects. The combination is highly strategic, positioning us as the largest hard rock lithium producer in the region, with immediate opportunities to progress a capital-efficient brownfield expansion of the NAL operation and other projects in the combined portfolio."