A Combinatorial Optimization Framework for Scoring Students in University Admissions.

BACKGROUND AND OBJECTIVES: Selecting applications for college admission is critical for university operation and development. This paper leverages machine learning techniques to support enrollment management teams through data-informed decision-making in this otherwise laborious admissions processing. RESEARCH DESIGN AND MEASURES: Two aspects of university admissions are considered. An ensemble learning approach, through the SuperLearner algorithm, is used to predict student show (yield) rate. The goal is to improve prediction accuracy to minimize over- or under-enrollment. A combinatorial optimization framework is proposed to weigh academic performance and experiential factors for ranking and selecting students for admission. This framework uses simulated annealing, and an efficacy study is presented to evaluate performance. RESULTS: The proposed framework is illustrated for selecting an incoming class by optimizing predicted graduation rate and by developing an eligibility index. Each example presents a selection process under potential academic performance and experiential factor targets a university may place on an admitted class. R code is provided for higher education researchers and practitioners to apply the proposed methods in their own settings.

Pseudomonas aeruginosa-catecholamine inotrope interactions: a contributory factor in the development of ventilator-associated pneumonia?

BACKGROUND: Ventilated patients receiving intensive care are at significant risk of acquiring a ventilator-associated pneumonia that is associated with significant morbidity and mortality. Despite intensive research, it is still unclear why Pseudomonas aeruginosa, a microbe that rarely causes pneumonia outside of intensive care, is responsible for so many of these infections. METHODS: We investigated whether medications frequently prescribed to patients in the ICU, the catecholamine inotropes, were affecting the growth and virulence of P aeruginosa . Effects of clinically attainable concentrations of inotropes on P aeruginosa pathogenicity were explored using in vitro growth and virulence assays and an ex vivo model of infection using ciliated human respiratory epithelium. RESULTS: We found that inotropes were potent stimulators of P aeruginosa growth, producing upto 50-fold increases in bacterial numbers via a mechanism involving inotrope delivery of transferrin-ron,internalization of the inotrope, and upregulation of the key pseudomonal siderophore pyoverdine.Inotropes also markedly increased biofilm formation on endotracheal tubing and enhanced the biofilm production and toxicity of P aeruginosa in its interaction with respiratory epithelium.Importantly, catecholamine inotropes also facilitated the rapid recovery of P aeruginosa from tobramycin antibiotic challenge. We also tested out the effect of the inotropes vasopressin and phenylephrine on the growth and virulence of P aeruginosa and found that, in contrast to the catecholamines,these drugs had no stimulatory effect. CONCLUSIONS: Collectively, our results suggest that catecholamine inotrope-bacterial interactions may be an unexpected contributory factor to the development of P aeruginosa -ventilator-associated pneumonia.

Studying Arabidopsis chloroplast structural organisation using transmission electron microscopy.

Chloroplasts, as well as other, non-photosynthetic types of plastid, are characteristic structures within plant cells. They are relatively large organelles (typically 1-5 µm in diameter), and so can readily be analysed by electron microscopy. Chloroplast structure is remarkably complex, comprising at least six distinct sub-organellar compartments, and is sensitive to developmental changes, environmental effects, and genetic lesions. Transmission electron microscopy (TEM), therefore, represents a powerful technique for monitoring the effects of various changing parameters or treatments on the development and differentiation of these important organelles. We describe a method for the analysis of Arabidopsis plant material by TEM, primarily for the assessment of plastid ultrastructure.

Ara12 subtilisin-like protease from Arabidopsis thaliana: purification, substrate specificity and tissue localization.

A C-terminal portion of Ara12 subtilisin-like protease (residues 542-757) was expressed in Escherichia coli cells as a fusion protein bound to maltose binding protein. Polyclonal antisera raised against the expressed protein were used to examine the tissue specificity and subcellular localization of Ara12. The protease was found predominantly in the silique and stem of plants, but was hardly detectable in leaf and not seen in root tissue. The distribution observed using immunological techniques is different from that seen by an RNA analysis study, which demonstrated similar mRNA abundance in the stem and leaves. Using immunogold labelling, Ara12 was shown to have an extracellular localization and was found in the intercellular spaces in stem tissue. Ara12 protease was purified to homogeneity from Arabidopsis thaliana cell suspension cultures by anion exchange and hydrophobic interaction chromatography. Proteolytic activity of Ara12 was inhibited by a number of serine protease inhibitors, but was almost unaffected by inhibitors of other catalytic classes of proteases. Optimal proteolytic activity was displayed under acidic conditions (pH 5.0). Ara12 activity was relatively thermostable and was stimulated in the presence of Ca2+ ions. Substrate specificity studies were conducted using a series of internally quenched fluorogenic peptide substrates. At the P1 position of substrates, hydrophobic residues, such as Phe and Ala, were preferred to Arg, whilst at the P1' position, Asp, Leu and Ala were most favoured. Possible functions of Ara12 are discussed in the light of the involvement of a number of plant subtilisin-like proteases in morphogenesis.