Grain boundary melting in ice.

We describe an optical scattering study of grain boundary premelting in water ice. Ubiquitous long ranged attractive polarization forces act to suppress grain boundary melting whereas repulsive forces originating in screened Coulomb interactions and classical colligative effects enhance it. The liquid enhancing effects can be manipulated by adding dopant ions to the system. For all measured grain boundaries this leads to increasing premelted film thickness with increasing electrolyte concentration. Although we understand that the interfacial surface charge densities q(s) and solute concentrations can potentially dominate the film thickness, we cannot directly measure them within a given grain boundary. Therefore, as a framework for interpreting the data we consider two appropriate q(s) dependent limits; one is dominated by the colligative effect and other is dominated by electrostatic interactions.

Light scattering from an isotropic layer between uniaxial crystals.

We develop a model for the reflection and transmission of plane waves by an isotropic layer sandwiched between two uniaxial crystals of arbitrary orientation. In the laboratory frame, reflection and transmission coefficients corresponding to the principal polarization directions in each crystal are given explicitly in terms of the [Formula: see text] axis and propagation directions. The solution is found by first deriving explicit expressions for reflection and transmission amplitude coefficients for waves propagating from an arbitrarily oriented uniaxial anisotropic material into an isotropic material. By combining these results with Lekner's (1991 J. Phys.: Condens. Matter3 6121-33) earlier treatment of waves propagating from isotropic media to anisotropic media and employing a matrix method we determine a solution to the general form of the multiple reflection case. The example system of a wetted interface between two ice crystals is used to contextualize the results.

Intensification of ice nucleation observed in ocean ship emissions.

Shipping contributes primary and secondary emission products to the atmospheric aerosol burden that have implications for climate, clouds, and air quality from regional to global scales. In this study we exam the potential impact of ship emissions with regards to ice nucleating particles. Particles that nucleate ice are known to directly affect precipitation and cloud microphysical properties. We have collected and analyzed particles for their ice nucleating capacity from a shipping channel outside a large Scandinavia port. We observe that ship plumes amplify the background levels of ice nucleating particles and discuss the larger scale implications. The measured ice nucleating particles suggest that the observed amplification is most likely important in regions with low levels of background particles. The Arctic, which as the sea ice pack declines is opening to transit and natural resource exploration and exploitation at an ever increasing rate, is highlighted as such a region.

Prediction of energy expenditure: simplified FAO/WHO/UNU factorial method vs continuous respirometry and habitual energy intake.

This study assessed a simple factorial method to predict energy expenditure (EE) in confined and free-living subjects. Thirteen subjects (seven male, 6 female) were studied on four occasions each. Measurements included BMR, 24-h EE by continuous respirometry, 4-d records of intake and activities, body weight, and urine collections. Agreement between measured and predicted 24-h EE was within +/- 2% for group results and +/- 10% for most individuals. Individual agreement was improved to within +/- 5% by using measured rather than predicted BMR. Habitual energy intake was 7.3% greater (p less than 0.05) than predicted EE in males and 5.1% less (NS) in females. Validatory data suggested overrecording of intake in males and underrecording in females. Large individual differences between habitual intake and predicted EE were observed but were significantly (p less than 0.01) correlated with both weight change and protein balance. Our simple factorial method provided acceptable estimates of EE in the subjects studied.

An iodine-125 plaque for radiotherapy of the eye: manufacture and dosimetric considerations.

A comparison of computer dose calculations and thermoluminescent dosemeter measurements in a phantom is given for an iodine-125 plaque for radiotherapy of the eye. The off-central-axis measurements and their relationship to the central-axis depth doses are documented. It was found that the gold backing of the applicator did not influence dosimetry in the phantom and thus the eye.

Cranial stereotactic multiple arc radiotherapy; treatment planning using angiographic images.

Stereotactic multiple arc radiotherapy (SMART) is an irradiation technique developed to treat small intracranial lesions. Calculation of absorbed-dose patterns for this treatment has traditionally involved complex computer programs incorporating algorithms designed to reconstruct the shape of the patient's head from computerized tomography (CT) images. A large proportion of the patients treated with SMART, however, have arteriovenous malformations for which angiography provides a better idea of lesion size and position than CT. This paper describes a computer program developed at St Bartholomew's Hospital which enables calculation of absorbed dose for a SMART treatment directly from angiographic radiographs, avoiding the need for CT. The program is compared with the existing CT-based treatment planning program.

Radiation properties of a miniature X-ray device for radiosurgery.

An alternative technology for performing interstitial intracranial radiosurgery is presented. Treatments are performed intraoperatively using a stereotactically mounted, miniature X-ray device. A concentrated, spherical pattern of X-rays is generated about the tip of a needle-like probe, which is inserted into the site of the lesion allowing the absorbed dose to healthy tissue to be minimized. A description of the device is given and results of investigations into the operating characteristics discussed.

Paediatric brachytherapy. II. Brain implantation.

The case histories of four children with brain tumours, for whom stereotactic brachytherapy was indicated, are presented from the St Bartholomew's Hospital intracranial brachytherapy programme. The recent evolution of the computed-tomography-directed stereotactic technique is described and the uses of different radionuclides (198Au, 192Ir) are discussed. The future of brachytherapy for paediatric brain tumours is debated.

Stereotactic multiple arc radiotherapy.

A radiotherapy technique is presented for delivering a concentrated pattern of absorbed dose to intracranial lesions. Treatment takes place on a conventional, isocentrically mounted linear accelerator, rotated in several planes around a single target site. A new, relocatable stereotactic frame is used which enables fractionated radiotherapy to be administered if required. Calculations of the absorbed dose distribution in three orthogonal planes are performed using specially prepared software on a computer used for standard treatment planning. In this way, the need for excessive computing power is avoided.

A direct optical method for the study of grain boundary melting.

The structure and evolution of grain boundaries underlies the nature of polycrystalline materials. Here we describe an experimental apparatus and light reflection technique for measuring disorder at grain boundaries in optically clear material, in thermodynamic equilibrium. The approach is demonstrated on ice bicrystals. Crystallographic orientation is measured for each ice sample. The type and concentration of impurity in the liquid can be controlled and the temperature can be continuously recorded and controlled over a range near the melting point. The general methodology is appropriate for a wide variety of materials.

The effect of smoking two cigarettes on resting metabolic rate with and without food.

Resting metabolic rate (RMR) was measured using a ventilated hood apparatus in 15 subjects before (BMR) and for 5 h after (5HEE) four treatments. In 10 smokers (five occasional and five habitual) the treatments were: food (600 kcal (2.51 MJ) breakfast) with and without smoking two cigarettes (F +/- S) and no food with and without smoking (NF +/- S). In five non-smokers duplicate measurements of food (F-S) and no food (NF-S) were made. In non-smokers the thermic effect of food (TEF) averaged 9.35 per cent of the ingested energy. Duplicate measures of 5HEE showed good reproducibility both with and without food (c.v. 2.5 and 1.3 per cent respectively). In smokers, RMR did not increase after smoking even during the first 15-30 min. There were no apparent differences in response between occasional and habitual smokers. 5HEE and delta 5HEE (5HEE minus BMR) were significantly lower after food with smoking than without smoking (-16 kcal (67 kJ)/5 h, P less than 0.001 and -14 kcal (59 kJ)/5 h, P less than 0.02 respectively) but not significantly lower after smoking without food. TEF was lower with smoking (8.6 per cent of ingested energy) than without smoking (10.0 per cent of ingested energy) but the difference was not significant (P = 0.23). TEF in smokers regardless of treatment averaged 9.3 per cent of the ingested energy. We conclude that any effects of smoking two cigarettes in isolation after overnight deprivation are too small or too variable to consistently influence RMR or the thermic effect of food.

No evidence for a chronic effect of smoking on energy expenditure.

OBJECTIVE: To investigate whether effects of smoking on energy expenditure (EE) extend chronically beyond smoking the last cigarette. DESIGN: Eight subjects (5M,3F) were studied over three consecutive months, after smoking as normal (S) on 1-3 occasions, and after not smoking for 4-8 weeks (NS) on 1-2 occasions. On each occasion subjects underwent one 32-h measurement of EE in a respiration chamber (8-h overnight plus a 24-h day, with no smoking in the chamber) and one measure of basal metabolic rate (BMR) on exit from the chamber. Statistical differences were determined using paired t-tests. RESULTS: There were no differences between S and NS for any of the EE measures, either including (n = 8) or excluding (n = 5) three subjects whose urinary cotinine excretions suggested failure to stop smoking during NS. For S and NS (N = 5) respectively, overnight EEs during the first night in the respiration chamber were 2.08 +/- 0.38 and 2.10 +/- 0.42 MJ/8-h; 24-h EEs during 12-36 hours after the last cigarette were 8.38 +/- 1.6 and 8.24 +/- 1.34 MJ/day, and BMRs were 6.51 +/- 1.21 and 6.50 +/- 1.07 MJ/day. CONCLUSION: We found no evidence for a chronic effect of smoking on EE.