The S&P/ASX 200 Index (ASX: XJO) is having a subdued start to the week. In afternoon trade, the benchmark index is down 0.4% to 8,174.1 points.

Four ASX shares that are not letting that hold them back are listed below. Here's why they are rising:

Appen Ltd (ASX: APX)

The Appen share price is up 12% to $1.98. This is despite there being no news out of the artificial intelligence data services company on Monday. However, it is worth noting that a big improvement in the company's performance has got investors excited recently. So much so, Appen's shares are now up more than 300% over the past two months. Last month, Appen released its half year results and revealed a $22.4 million improvement in its net loss after tax. It wouldn't be surprising if the company took advantage of this rally to raise funds and shore up its balance sheet further.

Lotus Resources Ltd (ASX: LOT)

The Lotus Resources share price is up 9% to 25 cents. This morning, analysts at Bell Potter reaffirmed their speculative buy rating on this uranium developer's shares with a reduced price target of 50 cents (from 70 cents). This suggests that its shares could double from current levels. In response to a disappointing scoping study, it said: "Despite this update, we continue to see material upside for LOT with the progression of Kayelekera which is due to recommence production over the coming year."

Opthea Ltd (ASX: OPT)

The Opthea share price is up 4.5% to 74.2 cents. This may have been driven by Opthea being added to the ASX 300 index this morning. It is a clinical-stage biopharmaceutical company developing novel therapies to treat highly prevalent and progressive retinal diseases. This includes wet age-related macular degeneration (wet AMD). CEO, Frederic Guerard, said: "Opthea's addition to the S&P/ASX 300 Index reflects the Company's strengthened balance sheet with proceeds from the recent financing completed in July 2024. We also reached a significant milestone by completing enrollment of close to 2,000 patients in the sozinibercept Phase 3 wet AMD program."

Paladin Energy Ltd (ASX: PDN)

The Paladin Energy share price is up over 7% to $10.11. Investors have been buying ASX uranium stocks on Monday after global giant Microsoft (NASDAQ: MSFT) turned to nuclear power to fuel its artificial intelligence ambitions. It has signed a deal with Constellation Energy (NASDAQ: CEG), which will help resurrect the Three Mile Island nuclear plant in Pennsylvania.