Following negative leads from offshore overnight, the S&P/ASX 200 (Index: ^AXJO) (ASX:XJO) is trading around 0.5% lower at 5140 points.

Investor sentiment is understandably negative as a result of the terrible attacks in Brussels overnight, although these four shares have charged higher today:

Programmed Maintenance Services Limited (ASX: PRG)

Shares of the staffing, maintenance and facility management services provider have gained more than 5.5% today following the announcement that it has secured a major infrastructure maintenance contract. The contract involves providing services to seven Western Australian government agencies for up to 15 years, with an initial term of five years and two five-year options. The contract is expected to generate revenue of between $90 million to $120 million per year with a total value in excess of $1.5 billion if the terms are renewed at each five-year period. Today’s news should provide some well needed respite for shareholders who have seen a 40% decline in the share price since the start of the year.

Ardent Leisure Group (ASX: AAD)

Shares of Ardent Leisure have gained 4.8% today, following on from yesterday’s strong performance. Investors are clearly pleased with the company’s decision to undertake a strategic review which will be focused on maximising the performance of the company’s domestic and US operations. As was reported yesterday, Ardent Leisure will sell its d’Albora Marinas business in a bid to free up capital to expand its Main Event business in the US. The company is also undertaking a number of other strategic initiatives it believes will help it to grow its entertainment operations in Australia including transforming its AMF bowling centres and additional development of the Dreamworld venue on the Gold Coast.

Sigma Pharmaceutical Limited (ASX: SIP)

Shares of the pharmaceutical wholesaler have traded gradually higher today following the release of its latest full year financial results. After hitting an intra-day low of 94 cents, the shares have rallied more than 8.5% to trade at $1.02. Sigma delivered revenue and underlying profit growth of 10.2% and 11.6%, respectively. Recent acquisitions and strong sales growth in over-the-counter pharmacy products helped to drive its latest result with PBS revenues continuing to lag. Management expects earning before interest and tax (EBIT) to increase by at least 5% each year for the next two years.

Woolworths Limited (ASX: WOW)

Shares of the supermarket giant have gained more than 1.8% today to trade at $22.47. The company has not released any market announcements today but it is interesting to note that rival Wesfarmers Ltd (ASX: WES) is also trading firmly higher today. This support is most likely coming from investors looking for defensive investments following the events overnight. Despite today’s gain, Woolworths shares have still lost around 22% of their value over the past 12 months.

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Motley Fool contributor Christopher Georges has no position in any stocks mentioned. Unless otherwise noted, the author does not have a position in any stocks mentioned by the author in the comments below. The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.