Microscopic aspects of crack propagation along PET-glass and PET-Al interfaces

This paper reports microscopic investigations of the propagation of cracks along polymer-glass and polymer-metal interfaces. The experimental methods include an asymmetric double cantilever beam in an optical microscope, and bire-fringence and atomic force microscopy of the crack faces. The crack fronts propagate inhomogeneously in space and time by way of forward bursts that spread laterally along the front over a certain distance. Experimental indications for correlation between crack propagation and interface roughness and for the occurrence of shear-bands in front of the propagating interface cracks are discussed. (c) 2006 Elsevier Ltd. All rights reserved

Local delamination on heavily deformed polymer-metal interfaces:evidence from microscopy

In this work the microstructure of interfaces present in heavily bi-axially deformed polymer-coated metal is studied. Cross sections of deformed polymer-coated steel are prepared using several polishing strategies, including the use of focused ion beam, and are imaged using optical microscopy and scanning electron microscopy. We find that the interfaces show significant details right down to the smallest scale observable with the preparation techniques used of about similar to 10 nm. Local delamination events at these deformed interfaces are observed and are found to be preferentially associated with overhanging parts on the interface. Overhanging parts are frequently observed, but only below a certain length-scale on the interfaces that are otherwise found to be self-affine up to a certain correlation length. The smallest detail includes the tail of the size distribution of the overhanging features. Together this suggests that the physical mechanisms determining the formation of critical features for adhesion operate at sub-grain level as well as at grain level

Quantitative measurement of sliding friction dynamics at mesoscopic scales: The lateral force apparatus

We describe an apparatus designed to quantitatively measure friction dynamics at the mesoscopic scale. This lateral force apparatus, LFA, uses double parallel leaf springs in leaf-spring units as force transducers and two focus error detection optical heads, optical heads, to measure deflections. The design of the leaf-spring units is new. Normal spring constants are in the range of 20–4000 N/m, and lateral spring constants are 7–1000 N/m. The optical heads combine a 10 nm sensitivity with a useful range of about 100 µm. The proven range of normal forces is 400 nN–150 mN. The leaf-spring units transduce friction and normal forces independently. Absolute values of normal and friction forces are calibrated. Typical errors are less than 10%. The calibration is partly in situ, for the sensitivity of the optical heads, and partly ex situ for the normal and lateral spring constants of the leaf-spring units. There is minimal coupling between the deflection measurements in the lateral and normal directions. This coupling is also calibrated in situ. It is typically 1% and can be as low as 0.25%. This means that the displacements of the tip can be measured accurately in the sliding direction and normal to the surface. Together, these characteristics make the LFA, well suited for quantitative study of friction dynamics at mesoscopic scales. Furthermore the design of the leaf-spring unit allows exchange of tips which may be fabricated (e.g., etched) from wire material (d0.4 mm) and can have customized shapes, e.g., polished flat squares. The ability of the LFA to study friction dynamics is briefly illustrated by results of stick-slip measurements on soft polymer surfaces

Exploring high-end climate change scenarios for flood protection of the Netherlands

This international scientific assessment has been carried out at the request of the Dutch Delta Committee. The "Deltacommissie" requested that the assessment explore the high-end climate change scenarios for flood protection of the Netherlands. It is a state-of–the art scientific assessment of the upper bound values and longer term projections (for sea level rise up to 2200) of climate induced sea level rise, changing storm surge conditions and peak discharge of river Rhine. It comprises a review of recent studies, model projections and expert opinions of more than 20 leading climate scientists from different countries around the North Sea, Australia and the US

Prospective clinical validation of the Eleveld propofol pharmacokinetic-pharmacodynamic model in general anaesthesia

BACKGROUND: Target-controlled infusion (TCI) systems incorporating pharmacokinetic (PK) or PK-pharmacodynamic (PK-PD) models can be used to facilitate drug administration. Existing models were developed using data from select populations, the use of which is, strictly speaking, limited to these populations. Recently a propofol PK-PD model was developed for a broad population range. The aim of the study was to prospectively validate this model in children, adults, older subjects, and obese adults undergoing general anaesthesia. METHODS: The 25 subjects included in each of four groups were stratified by age and weight. Subjects received propofol through TCI with the Eleveld model, titrated to a bispectral index (BIS) of 40-60. Arterial blood samples were collected at 5, 10, 20, 30, 40, and 60 min after the start of propofol infusion, and every 30 min thereafter, to a maximum of 10 samples. BIS was recorded continuously. Predictive performance was assessed using the Varvel criteria. RESULTS: For PK, the Eleveld model showed a bias < ±20% in children, adults, and obese adults, but a greater bias (-27%) in older subjects. Precision was <30% in all groups. For PD, the bias and wobble were <5 BIS units and the precision was close to 10 BIS units in all groups. Anaesthetists were able to achieve intraoperative BIS values of 40-60 using effect-site target concentrations about 85-140% of the age-adjusted Ce50. CONCLUSIONS: The Eleveld propofol PK-PD model showed predictive precision <30% for arterial plasma concentrations and BIS predictions with a low (population) bias when used in TCI in clinical anaesthesia practice

Clinical validation of pharmacokinetic/pharmacodynamic models for propofol infusion. Response to Br J Anaesth 2021:126: e172-4

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Opt-out as an acceptable method of obtaining consent in medical research: a short report

<p>Abstract</p> <p>Background</p> <p>A prospective cohort study was set up to investigate a possible association between antibiotic prescribing and antibiotic resistance of <it>E. coli </it>urinary tract infection in the community. Participation of patients with urinary tract infection was obtained through an opt-out methodology. This short paper reports on the acceptability of the opt-out recruitment approach.</p> <p>Methods</p> <p>Participating practices (22) were requested to send a urine sample from all patients presenting with symptoms of urinary tract infection. Upon receipt of the sample in the laboratory, a letter explaining the study, an opt-out form and a freepost envelope were sent to all adult patients. A website with additional information and including an 'opt-out' button was set up for the study.</p> <p>Results</p> <p>A total of 1362 urine samples were submitted by the 22 participating practices representing 1178 adult patients of whom 193 actively responded to the letter: 142 opted out by letter, 15 through the website, 2 by phone and 12 sent the letter back without indication, making a total of 171 patients or 14.5% opt-out; the remaining 22 patients (1.9%) explicitly opted in. The total group consisted of 80% women and the mean age was 50.9 years (sd 20.8). No significant differences were found between patients who participated and those who opted out in terms of age, gender or whether the urine sample was positive or not.</p> <p>Conclusions</p> <p>Overall the opt-out method was well received and participation in the study reached 85.5%. The low number of complaints (2) indicates that this is a generally acceptable method of patient recruitment. The 14.5% opt-out shows that it effectively empowers patients to decline participation. The similarity between patients opting out and the rest of the patients is reassuring for extrapolation of the results of the study.</p

Antimicrobial management and appropriateness of treatment of urinary tract infection in general practice in Ireland

<p>Abstract</p> <p>Background</p> <p>Urinary tract infections (UTIs) are the second most common bacterial infections in general practice and a frequent indication for prescription of antimicrobials. Increasing concern about the association between the use of antimicrobials and acquired antimicrobial resistance has highlighted the need for rational pharmacotherapy of common infections in general practice.</p> <p>Methods</p> <p>Management of urinary tract infections in general practice was studied prospectively over 8 weeks. Patients presenting with suspected UTI submitted a urine sample and were enrolled with an opt-out methodology. Data were collected on demographic variables, previous antimicrobial use and urine samples. Appropriateness of different treatment scenarios was assessed by comparing treatment with the laboratory report of the urine sample.</p> <p>Results</p> <p>A total of 22 practices participated in the study and included 866 patients. Bacteriuria was established for 21% of the patients, pyuria without bacteriuria for 9% and 70% showed no laboratory evidence of UTI. An antimicrobial agent was prescribed to 56% (481) of the patients, of whom 33% had an isolate, 11% with pyuria only and 56% without laboratory evidence of UTI. When taking all patients into account, 14% patients had an isolate identified and were prescribed an antimicrobial to which the isolate was susceptible. The agents most commonly prescribed for UTI were co-amoxyclav (33%), trimethoprim (26%) and fluoroquinolones (17%). Variation between practices in antimicrobial prescribing as well as in their preference for certain antimicrobials, was observed. Treatment as prescribed by the GP was interpreted as appropriate for 55% of the patients. Three different treatment scenarios were simulated, i.e. if all patients who received an antimicrobial were treated with nitrofurantoin, trimethoprim or ciprofloxacin only. Treatment as prescribed by the GP was no more effective than treatment with nitrofurantoin for all patients given an antimicrobial or treatment with ciprofloxacin in all patients. Prescribing cost was lower for nitrofurantoin. Empirical treatment of all patients with trimethoprim only was less effective due to the higher resistance levels.</p> <p>Conclusions</p> <p>There appears to be considerable scope to reduce the frequency and increase the quality of antimicrobial prescribing for patients with suspected UTI.</p

Dietary options to reduce the environmental impact of milk production

A range of options was explored to test the hypothesis that diets for dairy cows could be formulated to reduce the carbon footprint (CFP) of feed, increase efficiency of conversion of potentially human-edible feed into milk, increase nitrogen use efficiency (NUE) and reduce methane (CH4) emissions per kg milk. Diets based on grazed grass, grass silage, maize silage or straw, supplemented with raw material feeds, were formulated to meet requirements for metabolizable energy and metabolizable protein for a range of daily milk yields. At similar levels of milk yield, NUE, predicted CH4 emissions and diet CFP were generally higher for diets based on maize silage than for those based on grazed grass, grass silage or straw. Predicted CH4 emissions and human-edible proportion decreased, while NUE increased with the increasing level of milk yield. It is concluded that there is potential to reduce the environmental impact of milk production by altering diet formulation, but the extent to which this might occur is likely to depend on availability of raw material feeds with low CFPs

Numerical Investigation of Pyrolysis Gas Blowing Pattern and Thermal Response using Orthotropic Charring Ablative Material

An orthotropic material model is implemented in a three-dimensional material response code, and numerically studied for charring ablative material. Model comparison is performed using an iso-Q sample geometry. The comparison is presented using pyrolysis gas streamlines and time series of temperature at selected virtual thermocouples. Results show that orthotropic permeability affects both pyrolysis gas flow and thermal response, but orthotropic thermal conductivity essentially changes the thermal performance of the material. The effect of orthotropic properties may have practical use such that the material performance can be manipulated by altering the angle of orthotropic orientation