Petrocalc Corporation is not directly linked to the website provided (http://www.mcsi.com/), as this URL typically would not connect to a company named Petrocalc Corporation based on the URL format and naming. If Petrocalc Corporation is a hypothetical or real company you're inquiring about, please provide additional context or correct details. If you meant to inquire about the company associated with the provided URL, please confirm or correct it as well. For an accurate description of any company, including its main activities, industry focus, and other relevant details, further specific information or the correct website would be necessary.