Ambrian Capital slumped to a 52-week low after a trading update littered with references to subdued markets and downward adjustments to the book value of its investments which will cause the company to report a substantial pre-tax loss.The natural resources investment firm upped the size of the write-down it expects to make on its soon to be sold investment in Ambrian Partners Limited (APL) to about £2m, having previously estimated the hit would be in the region of £1.5m.As for the company's commodity operations, they were hit by the global slow-down in the second half of 2011. Market conditions have also affected the value of the company's principal investments in public and private resource-based mining, exploration and service companies resulting in a loss of around £1m during the second half of 2011.North River Resources, the AIM listed resource company focused on Southern Africa, confirmed it has coughed up the $800,000 required to take a 50% stake in Brandberg Energy, the joint venture set up with Extract Resources for the purpose of holding exclusive prospecting licences 3327 and 3328 in Namibia. Brandberg now has the readies in the bin to enable it to complete a 1,100 metre drill programme planned by Extract Resources, and North River said the drilling programme may be extended to 1,500 - 2,000 metres.Ark Therapeutics has received a US patent for the structures of candidate compounds in its Neuropilin-1 receptor small molecule antagonist programme. The product inhibits both tumour growth and the development of the tumour blood supply. Formal grant of the patent is expected in two months. Shares rose 4.23% to 3.70p. James Cropper, a specialist paper and materials group, expects pre-tax profits (excluding pension adjustments) in the year to March 31st, 2012, to be more or less unchanged from last year, after it revealed sales at its Speciality Papers and Converting units will be significantly lower than previously expected. DCD Media has released a statement in response to Timeweave's purchase of £3m-worth of convertible loan notes in the company, saying it "looks forward to arranging a meeting with Timeweave in due course to seek to understand better Timeweave's rationale and intentions in making this investment." The total consideration for the acquired debt, which was satisfied by Timeweave's existing cash reserves, was £2.087m. Sarantel Group, a manufacturer of miniature filtering antennas for mobile and wireless devices, has received its largest order to date from a leading military radio manufacturer for a range of different Sarantel antenna products. The order, which is part of a multi-year supply contract, is expected to be delivered over the next 12 months and will have a significant impact on Sarantel's revenues and cash flow in the current financial year, the firm said. Shares rose 21.62% to 0.68p.Oil company Aerte has reported that both of the updated versions of its product ranges are now in production and that it has received the first order for 3,200 devices, worth £0.22m. "We are now very focused on selling the new product range and expanding into further territories," the firm said. Shares gained 5% to 0.62p.