An air-filled cavity in a dense portion of a skull bone. The sinuses decrease the weight of the skull. The sinuses are formed in four right-left pairs. The frontal sinuses are positioned behind the forehead, while the maxillary sinuses are behind the cheeks. The sphenoid and ethmoid sinuses are deeper in the skull behind the eyes and maxillary sinuses. The sinuses are lined by mucous-secreting cells. Air enters the sinuses through small opening in bone called ostia. If an ostium is blocked, air cannot pass into the sinus and likewise mucous cannot drain out. Open access to the scientific literature means the removal of barriers (including price barriers) from accessing scholarly work. There are two parallel âroadsâ towards open access: Open Access articles and self-archiving. Open Access articles are immediately, freely available on their Web site, a model mostly funded by charges paid by the author (usually through a research grant).
Open Access raises practical and policy questions for scholars, publishers, funders, and policymakers alike, including what the return on investment is when paying an article processing fee to publish in an Open Access articles, or whether investments into institutional repositories should be made and whether self-archiving should be made mandatory, as contemplated by some funders.
Last date updated on September, 2014