Influence of Polyglycidyl-type Bonding Agents on the Viscoelastic Properties of a Carboxyl-terminated Poly(butadiene-co-acrylonitrilе)-based Composite Rocket Propellant

In the present study, functionally substituted bonding agents (triglycidyl isocyanurate and diglycidyl dimethylhydantoin) were incorporated into a composite propellant formulation based on carboxyl-terminated poly(butadiene-co-acrylonitrilе) and ammonium perchlorate. Bonding agents are an important component of a composite propellant, making up to 0.5 wt.% of the formulation. They affect processing, mechanical properties, ballistics, ageing and the characteristics of insensitive munition (IM) propellants. All of the testing has been done using an unmetallized propellant formulation (80 wt.% bimodal ammonium perchlorate and 20 wt.% binder). The focus has been on the mechanical properties of the propellant, as influenced by the presence of these bonding agents. Mechanical uniaxial tensile tests were accompanied by a dynamic mechanical analysis (DMA) over a wide range of temperatures. The storage modulus, loss modulus, loss factor and glass transition temperature for each propellant sample have been evaluated. The network characteristics, such as sol-gel content and crosslink density have been calculated and successfully correlated with the mechanical properties. The dynamic mechanical studies showed that the content of the bonding agent did not influence the glass transition temperature; however, the loss factor was shown to be a function of the crosslink density

Rotational Spectrum and Internal Dynamics of Methylpyruvate

The rotational spectra of five isotopologues (normal and all monosubstituted 13C species) of methylpyruvate have been measured with the pulsed jet Fourier transform microwave technique. Rotational transitions are split into quintets due to the internal rotations of the two methyl groups. The corresponding barriers to internal rotation have been determined to be V3(H3C-O) = 4.883(8) kJ mol-1 and V3(H3C-C) = 4.657(8) kJ mol-1, respectively. Information on the skeletal heavy atom structure has been obtained from the 15 available rotational constants

Sensing the Molecular Structures of Hexan‐2‐one by Internal Rotation and Microwave Spectroscopy

International audienceUsing two molecular jet Fourier transform spectrometers, the microwave spectrum of hexan-2-one, also called methyl n-butyl ketone, was recorded in the frequency range from 2 to 40 GHz. Three conformers were assigned and fine splittings caused by the internal rotations of the two terminal methyl groups were analyzed. For the acetyl methyl group CH3COC3H6CH3, the torsional barrier is 186.9198(50) cm−1 , 233.5913(97) cm−1 , and 182.2481(25) cm−1 for the three observed conformers, respectively. The value of this parameter could be linked to the structure of the individual conformer, which enabled us to create a rule for predicting the barrier height of the acetyl methyl torsion in ketones. The very small splittings arising from the internal rotation of the butyl methyl group CH3COC3H6CH3 could be resolved as well, yielding the respective torsional barriers of 979.99(88) cm−1 , 1016.30(77) cm−1 , and 961.9(32) cm−1

Mortality after surgery in Europe: a 7 day cohort study

Background: Clinical outcomes after major surgery are poorly described at the national level. Evidence of heterogeneity between hospitals and health-care systems suggests potential to improve care for patients but this potential remains unconfirmed. The European Surgical Outcomes Study was an international study designed to assess outcomes after non-cardiac surgery in Europe.Methods: We did this 7 day cohort study between April 4 and April 11, 2011. We collected data describing consecutive patients aged 16 years and older undergoing inpatient non-cardiac surgery in 498 hospitals across 28 European nations. Patients were followed up for a maximum of 60 days. The primary endpoint was in-hospital mortality. Secondary outcome measures were duration of hospital stay and admission to critical care. We used χ² and Fisher’s exact tests to compare categorical variables and the t test or the Mann-Whitney U test to compare continuous variables. Significance was set at p<0·05. We constructed multilevel logistic regression models to adjust for the differences in mortality rates between countries.Findings: We included 46 539 patients, of whom 1855 (4%) died before hospital discharge. 3599 (8%) patients were admitted to critical care after surgery with a median length of stay of 1·2 days (IQR 0·9–3·6). 1358 (73%) patients who died were not admitted to critical care at any stage after surgery. Crude mortality rates varied widely between countries (from 1·2% [95% CI 0·0–3·0] for Iceland to 21·5% [16·9–26·2] for Latvia). After adjustment for confounding variables, important differences remained between countries when compared with the UK, the country with the largest dataset (OR range from 0·44 [95% CI 0·19 1·05; p=0·06] for Finland to 6·92 [2·37–20·27; p=0·0004] for Poland).Interpretation: The mortality rate for patients undergoing inpatient non-cardiac surgery was higher than anticipated. Variations in mortality between countries suggest the need for national and international strategies to improve care for this group of patients.Funding: European Society of Intensive Care Medicine, European Society of Anaesthesiology