Photodynamic Activity on Biofilm in Endotracheal Tubes of Patients Admitted to an Intensive Care Unit

Ventilator-associated pneumonia (VAP) is an infection that arises after endotracheal intubation affecting patients under intensive care. The presence of the endotracheal tube (ETT) is a risk factor since it is colonized by multispecies biofilm. Antimicrobial photodynamic therapy (aPDT) could be a strategy to decontaminate ETTs. We verify if methylene blue (MB) associated with external illumination of the ETT could be an alternative to destroy biofilm. We performed an in vitro and ex vivo study. In vitro study was performed with P. aeruginosa biofilm grew over ETT for 7 days. After treatment, the surviving cells were cultured for 3 days and the biofilm was analyzed by crystal violet absorbance. Ex vivo study employed ETT obtained from extubated patients. aPDT was performed with MB (100 µm ) and red LED (λ = 640±20 nm). We quantified the biofilm thickness and used scanning electron microscopy and fluorescence technique to verify morphological and functional changes after aPDT. Our results showed that bacteria remain susceptible to aPDT after sequential treatments. We also attested that aPDT can reduce biofilm thickness, disrupt biofilm attachment from ETT surface and kill microbial cells. These data suggest that aPDT should be investigated to decrease VAP incidence via ETT decontamination.     

Competition between Liquid-liquid De-mixing,Crystallization, and Glass Transition in Solutions of PLA of Different Stereochemistry and DEET

Liquid-liquid(L-L)de-mixing and vitrification of solutions of either crystallizable poly(L-lactic acid)(PLLA)or non-crystallizable poly(D/L-lactic acid)(PDLLA)with 50 m%N,N-diethyl-3-methylbenzamide(DEET)were analyzed by calorimetry and cloud-point measurements,which allows drawing conclusions about the effect of polymer stereochemistry on the phase behavior.Regardless of the PLA stereochemistry,vitrification of the solutions on fast cooling,hindering crystallization of PLLA,occurred below-20℃ and suppressed prior L-L de-mixing.The experimental results prove that crystallization in samples containing crystallizable PLLA,observed at around 55℃ on slow cooling,is not preceded by L-L de-mixing.     

Circular colorings of weighted graphs

Suppose that G is a finite simple graph and w is a weight function which assigns to each vertex of G a nonnegative real number. Let C be a circle of length t. A t-circular coloring of (G, w) is a mapping Δ of the vertices of G to arcs of C such that Δ(x)∩Δ(y) = 0 if (x, y) ∈ E(G) and Δ(x) has length w(x). The circular-chromatic number of (G, w) is the least t for which there is a t-circular coloring of (G, w). This paper discusses basic properties of circular chromatic number of a weighted graph and relations between this parameter and other graph parameters. We are particularly interested in graphs G for which the circular-chromatic number of (G, w) is equal to the fractional clique weight of (G, w) for arbitrary weight function w. We call such graphs star-superperfect. We prove that odd cycles and their complements are star-superperfect. We then prove a theorem about the circular chromatic number of lexicographic product of graphs which provides a tool of constructing new star-superperfect graphs from old ones. © 1996 John Wiley & Sons, Inc.     

Pur - sandwich panels in the building industry - development of fire regulations in Europe

The European Community aims to harmonize standards for fire safety of building products. The report starts with an overview of the existing different testing methods for sandwich panels with PUR-rigid-foam core and metal facings. For harmonization of the fire standards experts are looking for a robust longtime solution, which shall have a better relation to the end-use conditions of the building products. First results of proposed ISO-Room/Corner-Tests for PUR-sandwich panels are discussed.