A comprehensive review on zeolite-based mixed matrix membranes for CO2/CH4 separation.

Biogas consisting of carbon dioxide/methane (CO2/CH4) gas mixtures has emerged as an alternative renewable fuel to natural gas. The presence of CO2 can decrease the calorific value and generate greenhouse gas. Hence, separating CO2 from CH4 is a vital step in enhancing the use of biogas. Zeolite and zeolite-based mixed matrix membrane (MMM) is considered an auspicious candidate for CO2/CH4 separation due to thermal and chemical stability. This review initially addresses the development of zeolite and zeolite-based MMM for the CO2/CH4 separation. The highest performance in terms of CO2 permeance and CO2/CH4 selectivity was achieved using zeolite and zeolite-based MMM, which exhibited CO2 permeance in the range of 2.0 × 10- 7-7.0 × 10- 6 mol m- 2 s- 1 Pa- 1 with CO2/CH4 selectivity ranging from 3 to 300. Current trends directed toward improving CO2/CH4 selectivity via modification methods including post-treatment, ion-exchanged, amino silane-grafted, and ionic liquid encapsulated of zeolite-based MMM. Those modification methods improved the defect-free and interfacial adhesions between zeolite particulates and polymer matrices and subsequently enhanced the CO2/CH4 selectivity. The modifications via ionic liquid and silane methods more influenced the CO2/CH4 selectivity with 90 and 660, respectively. This review also focuses on the possible applications of zeolite-based MMM, which include the purification and treatment of water as well as biomedical applications. Lastly, future advances and opportunities for gas separation applications are also briefly discussed. This review aims to share knowledge regarding zeolite-based MMM and inspire new industrial applications.

The value of prostate-specific antigen in Asia.

One of the most important diagnostic tools used to detect prostate cancer is prostate-specific antigen (PSA), yet increased PSA alone does not reflect the presence of prostate cancer. Other pathological prostatic conditions such as prostatitis and benign prostatic hyperplasia (BPH) may also increase the level of PSA. However, unlike in other prostate diseases, PSA has a key role in the diagnosis and management of prostate cancer. The incidence of prostate cancer varies from country to country, with the highest incidence being found in the Western world and the lowest in Asian countries. Owing to the low incidence of prostate cancer, there could be different views regarding the use of PSA in Asian countries, especially for the early detection/screening of prostate cancer. The purpose of this article is to review the use and value of PSA in the diagnosis of prostate diseases (especially prostate cancer) in Asian countries/populations. A literature search was performed in 'MEDLINE' (PubMed) and Google Scholar using main keywords such as 'PSA', 'PSA usage', 'PSA sensitivity and specificity', 'Asia', and various countries in Asia. Articles that provide population/community-based PSA data, together with the characteristics, distribution, and indications for PSA testing in the respective countries, were selected. Eleven papers were finally selected for inclusion in this review. Five studies found that PSA, by its 95th percentile value, have an age-referenced tendency in Asian males, similarly to the West. The predictive values of PSA in detecting prostate cancer are also quite similar to those in Western countries. With the exponential growth of the aging population in the world, especially in Asia, the incidence of prostate cancer will follow this upward trend. Therefore, PSA testing for screening or diagnostic purposes would increase with time in Asia.

Cytotoxic strains of Pseudomonas aeruginosa can damage the intact corneal surface in vitro.

PURPOSE: Although the corneal epithelial cell layer is believed to serve as a barrier against most types of bacteria, certain strains of P. aeruginosa have been shown to kill corneal epithelial cells in primary cultures. The aim of this study was to test whether these strains could damage epithelia on uninjured whole corneas. METHODS: Five-week-old Sprague-Dawley rats were sacrificed and their eyes were placed in organ culture. The corneal surface of each eye was incubated with 8 microL of media alone or a bacterial suspension containing 8 x 10(6) cfu of one of 12 cytotoxic and noncytotoxic strains of P. aeruginosa for 3 hours at 35 degrees C. Trypan blue was then added to visualize surface epithelial cell injury. A masked observer examined each cornea under a dissecting microscope and assigned a score of between 1 and 3 to describe the extent of injury. RESULTS: Cytotoxic P. aeruginosa injured the surface epithelium. The extent of injury induced by the various strains correlated with previously published in vitro measures of cytotoxic capacity toward cultured corneal epithelial cells. Cytotoxicity required at least 2 hours of bacterial contact and was dependent upon ExsA, a transcriptional activator of several genes in P. aeruginosa, including the gene encoding exoenzyme S. CONCLUSIONS: Cytotoxic P. aeruginosa strains can damage epithelia on an uninjured corneal surface providing there is prolonged bacterial contact. Stagnation of cytotoxic bacteria against the corneal surface may contribute to the pathogenesis of infection associated with the use of soft contact lenses.