Using sliding mode observers to estimate BtuB concentration from measured vitamin B12 concentration.

A simple model for the B12-riboswitch regulatory network in Escherichia coli is first described and the same analysis is applied when changing the strain to Salmonella enterica. Model validation is undertaken by linking the dynamics of the riboswitch model to bacterial growth and comparing the results obtained with in vivo experimental measurements. Measurements of bacterial growth are relatively straightforward to obtain experimentally, but experimental measurements relating to the operation of the riboswitch are more difficult. Using the validated model, sliding mode observer design methods are used to estimate BtuB given measurements of the concentration of vitamin B12. The sliding mode approach is selected because of its inherent robustness properties as well as for the ease of implementation. Validation of the estimates of BtuB produced by the observer is undertaken by comparing the BtuB and vitamin B12 concentrations estimated from the observer with green fluorescent protein production and the concentration of vitamin B12 obtained experimentally. These experimental results also provide further validation of the underpinning mathematical model. The results establish that using a sliding mode observer as a soft sensor is a useful approach to explore the operation of a vitamin B12 riboswitch given measurements of the concentration of vitamin B12.

Guidelines for the Topical Treatment of Psoriasis Vulgaris in the Levant and Iraq Area.

Psoriasis vulgaris is a common chronic, inflammatory, multisystem disorder that affects approximately 1.5% to 3.4% of the population in the Middle East. The disease has an impact on the quality of life in a significant number of affected patients. The majority of patients (approximately 70%) have mild to moderate psoriasis that is manageable with topical agents, which generally show a high efficacy to safety ratio. Topical agents can be used alone when treating patients with limited disease or may be used as adjunctive therapy for patients with more extensive psoriasis undergoing systemic treatment. Treatment should also be customized to meet individual patients' needs. To optimize the topical treatment of psoriasis in the Levant and Iraq area, dermatology experts from Iraq, Jordan, Lebanon, Palestine, and Syria met and initiated a project to develop guidelines and recommendations for the topical management of psoriasis. The guidelines are based on literature evidence and experts' opinions. We present recommendations for the use of topical corticosteroids, vitamin D analogues, calcineurin inhibitors, tazarotene, salicylic acid, anthralin, and coal tar, as well as combination therapy, based on their efficacy and safety profiles.