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Let M n ( F ) be the set of all n × n matrices over the field F , where F = R or F = C . We characterize maps on M n ( F ) which are surjective and preserve either the left-star or the right-star order in both directions, but are not necessarily additive.

The aim of this study was to compare the effect of closed versus open endotracheal suction systems on the development of ventilator-associated pneumonia (VAP). A prospective, randomized, controlled trial was performed in a medical intensive care unit (MICU) of a university hospital in patients who received mechanical ventilation for more than 48 h. Patients were randomized to receive endotracheal suction with either closed catheters (closed suction group; N-41) or single-use catheters (open suction group; N=37). Cultures were taken from the ventilator tubing of 42 patients to determine the rate of colonization. There was no difference between the groups in terms of the frequency of development of VAP, mortality in the MICU, length of MICU stay and duration of mechanical ventilation. Thirteen patients in the open suction group and 16 patients in the closed suction group became colonized (P=0.14). The colonization rates by Acinetobacter spp. and Pseudomonas aeruginosa were more frequent in the closed suction group than in the open suction group (P

The management of hospital-acquired pneumonia (HAP) presents a major challenge for the clinician. The insensitivity of current diagnostic methods and the increasing prevalence of nosocomial pathogens with multiple antibiotic resistance complicate the issue. Use of mechanical ventilation and broad-spectrum antimicrobials in the intensive care setting predipose patients to acquire HAP more frequently with antimicrobial-resistant pathogens. Controversy exists regarding the patients in which invasive diagnostic testing is indicated; the timing of these procedures is another subject of debate. Proper empirical therapy is fundamental to a favourable outcome, and the selection of inappropriate agents to which pathogens are resistant contributes significantly to morbidity and mortality. In general, there is agreement on the requirement for a thorough knowledge of the local causative organisms and the pathogens' resistance profiles. A wide variety of antimicrobials can be used either as monotherapy or in combinations.

Let R be a commutative domain and let M be an R-module. It is proved that to every prime submodule of M there corresponds a prime ideal of R and a set of linear equations of a certain type, and conversely. In particular, in case M is a finitely generated R-module generated by n elements, for some positive integer n, then the prime submodules of M are given by prime ideals of R and certain finite systems of equations containing at most n equations.