Comparing very low birth weight versus very low gestation cohort methods for outcome analysis of high risk preterm infants

© 2017 The Author(s). Background: Compared to very low gestational age (<32 weeks, VLGA) cohorts, very low birth weight (<1500 g; VLBW) cohorts are more prone to selection bias toward small-for-gestational age (SGA) infants, which may impact upon the validity of data for benchmarking purposes. Method: Data from all VLGA or VLBW infants admitted in the 3 Networks between 2008 and 2011 were used. Two-thirds of each network cohort was randomly selected to develop prediction models for mortality and composite adverse outcome (CAO: mortality or cerebral injuries, chronic lung disease, severe retinopathy or necrotizing enterocolitis) and the remaining for internal validation. Areas under the ROC curves (AUC) of the models were compared. Results: VLBW cohort (24,335 infants) had twice more SGA infants (20.4% vs. 9.3%) than the VLGA cohort (29,180 infants) and had a higher rate of CAO (36.5% vs. 32.6%). The two models had equal prediction power for mortality and CAO (AUC 0.83), and similarly for all other cross-cohort validations (AUC 0.81-0.85). Neither model performed well for the extremes of birth weight for gestation (<1500 g and ≥32 weeks, AUC 0.50-0.65; ≥1500 g and <32 weeks, AUC 0.60-0.62). Conclusion: There was no difference in prediction power for adverse outcome between cohorting VLGA or VLBW despite substantial bias in SGA population. Either cohorting practises are suitable for international benchmarking

Hydromechanical characterization of fractures close to a tunnel opening: A case study

Important factors influencing the hydromechanical behavior of a fracture are in situ rock stresses (natural and induced) as well as hydraulic heads, fracture orientation, connectivity and fracture geometry, including their infillings. Particular attention is given to larger, water-conducting fractures that intersect or are close to a tunnel. For the Bentonite Rock Interaction Experiment (BRIE) at the \uc4sp\uf6 Hard Rock Laboratory (HRL) in Sweden, the interaction between rock and bentonite in a deposition borehole is of particular interest. The BRIE experiment is being conducted at a depth of 420 meters in crystalline rock. This paper presents results from the initial identification, characterization and modeling of a small number of fractures close to the tunnel opening. So far, these fractures have been identified as the most important water-conducting fractures. In this identification and characterization exercise, core-drilled, vertical, three-meter deep investigation boreholes were made in the tunnel floor. Logging of natural hydraulic heads in boreholes and hydraulic tests, along with borehole and tunnel mapping in combination with modeling, indicate small deformations. This was also confirmed by deformation measurements performed in the boreholes. The description of the site will be further updated and revised and additional investigations into the link between stress history, fracture geometry and selection of fracture mechanical properties will be of particular interest

Rationalizing cellulose (in)solubility: reviewing basic physicochemical aspects and role of hydrophobic interactions

Despite being the world's most abundant natural polymer and one of the most studied, cellulose is still challenging researchers. Cellulose is known to be insoluble in water and in many organic solvents, but can be dissolved in a number of solvents of intermediate properties, like N-methylmorpholine N-oxide and ionic liquids which, apparently, are not related. It can also be dissolved in water at extreme pHs, in particular if a cosolute of intermediate polarity is added. The insolubility in water is often referred to strong intermolecular hydrogen bonding between cellulose molecules. Revisiting some fundamental polymer physicochemical aspects (i.e. intermolecular interactions) a different picture is now revealed: cellulose is significantly amphiphilic and hydrophobic interactions are important to understand its solubility pattern. In this paper we try to provide a basis for developing novel solvents for cellulose based on a critical analysis of the intermolecular interactions involved and mechanisms of dissolution