Optical analysis of crack tip stress fields: a comparative study

Four optical techniques for evaluating stress intensity factors in opaque specimens are described in outline, and compared for both an artificial crack and a fatigue crack. The results are compared to a standard solution for the geometry considered. All the techniques gave acceptable results over a range of stress levels and crack lengths. The methods of caustics and strain gauges were less good, whilst photoelasticity gave consistent results over a wide range of stress levels. Comments on the ease of application and the resource implications are also made in order to assist practitioners.     

PREDICTION OF VICTIMIZATION FROM AN INSTRUMENTAL CONDITIONING PROCEDURE.

PRESENTS A DESCRIPTION OF AN INSTRUMENTAL CONDITIONING APPARATUS DESIGNED TO SERVE AS A PERSONALITY ASSESSMENT PROCEDURE. IN THIS PROCEDURE, A VISUAL STIMULUS WAS MADE CONTINGENT UPON A LEVER-PRESSING RESPONSE. THE MAGNITUDE OF THE CHANGE IN RATE OF RESPONDING CONSTITUTED THE DEPENDENT MEASURE. THE STIMULI CONSISTED OF CARTOONS PORTRAYING SOCIAL BEHAVIORS THAT HAD IN THE PAST FOR THE CHILDREN STUDIED BEEN ASSOCIATED AS CONDITIONED STIMULI FOR PAIN. EACH OF THE SS WAS OBSERVED OVER A 5-WK PERIOD IN A NURSERY SCHOOL SETTING. THE NUMBER OF OCCASIONS ON WHICH EACH CHILD WAS VICTIMIZED BY AN AGGRESSOR WAS RECORDED. IT WAS PREDICTED AND CONFIRMED THAT CHILDREN WHO HAD BEEN MORE FREQUENTLY VICTIMIZED WOULD SHOW A GREATER IMPAIRMENT IN THE RATE OF RESPONDING WHEN SUCH STIMULI WERE MADE CONTINGENT UPON LEVER PRESSING. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tropical lake surface temperatures from locally received NOAA-11 AVHRR d— comparison with in situ measurements

The estimation of tropical lake surface temperature from locally received NOAA AVHRR data was investigated. The applicability of published sea surface temperature algorithms in estimating the tropical lake surface temperature of Lake Malawi was confirmed; the most accurate algorithm being that of McClain et al( 1985) with a root mean square deviation of 0-45 K. Other published algorithms tested required localised bias correction. Newly derived algorithms showed the advantage of the triple window approach, with a correlation coefficient of 0-92 between the estimated and measured temperatures.     

Effect of irradiation and modified atmosphere packaging on the microbiological and sensory quality of pork stored at refrigeration temperatures

The effect of combining low-dose irradiation (1.75 kGy) with modified atmosphere packaging (MAP) on the microbiological and sensory quality of pork chops stored at refrigeration temperatures was studied. The microflora of irradiated MAP pork was almost exclusively composed of lactic acid bacteria, predominantly Lactobacillus spp. Modified atmospheres containing either 25 or 50% CO₂, balance N₂, resulted in the best microbial control in irradiated pork held at 4°C, compared to an unirradiated MAP control, and these atmospheres were subsequently used in sensory studies. The atmosphere containing 25% CO₂ 75% N₂ maintained the uncooked colour and odour of irradiated pork chops more effectively than 50% CO₂ 50% N₂. Therefore packaging in a modified atmosphere containing 25% CO₂, balance N₂, followed by irradiation to a dose of 1.75 kGy is recommended to improve the microbiological and sensory quality of pork chops.     

Photoconductivity and Fading

The conductivity of purified films of the eight dyes used in the ISO Light-fastness Test have been studied both in the dark and under illumination by the visible and ultra-violet radiation from a mercury vapour lamp. All eight dyes behaved as n-type semiconductors and additionally those of light fastness ratings five and above showed p-type semiconduction. All the dyes also behaved as photoconductors and the activation energies of photoconduction were between one third and one fifth of those for semiconduction. Very rapid response to illumination was shown by the dyes of highest light fastness. Although the dyes were of five different chemical types, some tentative rules relating properties to light fastness can be formulated. These are: (1) Dyes should show p-type and n-type semicon-ductivity. (2) Response time of photo-conduction should be short. (3) In the case of dyes of similar structure, higher activation energies for photoconduction favour higher light fastness.     

Molecular Mechanisms of Disperse Dyeing of Polyester and Nylon Fibres

The kinetics of the dyeing of polyester fibres with disperse dyes have previously been discussed in terms of a model in which the only forces of interaction between dye and polymer are those that give rise to mutual solubility. The rate and extent of dyeing depend on the size and shape of the dye molecules and the detailed structure of the fibre. The concentration profiles of dye within single filaments of polyesters and nylons have now been determined by a new method termed ‘optical sectioning’, in which an image of a filament is scanned by a narrow slit. The dye distributions are found by comparing experimental transmission values with those calculated by a computer for a model system in which various parameters can be adjusted. For the polyester-dye systems the rate constant of transfer of dye from dyebath to fibre (k₁) was the same as the rate constant of diffusion away from the interface (k₂). Some nylon-dye systems, on the other hand, behaved as if k₂ = k₁, whereas others behaved initially as if k₁ = k₂ but later as if k₂ > k₁. Apparent diffusion coefficients were also derived from sorption measurements and were found to fall as the dye concentration in the fibre increased. Measurement of the orientation of the dye molecules by optical dichroism showed that the dye molecules entering the filaments late in the dyeing process were more highly orientated than the earlier ones. The decrease in diffusion coefficient has been interpreted in terms of the observed higher orientation, as resulting from a greater entropy of activation in the diffusion process.     

Assessment of the previous heat treatment given to meat products in the temperature range 40°–90°C. Part 1: Soluble nitrogen analysis

The aim of this work was to identify a technique which would yield information retrospectively about the heat treatment applied to a meat product in the temperature range 40–90°C. Saline extracts of beef samples ( M. longissimus dorsi and M. semi-membranosus ) of known heat treatment, were analysed for soluble nitrogen by Kjeldahl analysis. The amount of residual soluble nitrogen in an extract was found to decrease as the cooking temperature increased, with the major reduction occurring between 40 and 70°C. A good correlation between nitrogen values was obtained for aliquots removed from a continuously heated raw meat extract, 5 mm slices and the centre sections of 60 mm cubes. It was also possible to detect differences in the extent of heating achieved at points between the surface and the centre of the solid piece of meat. These results indicate that it may be possible to estimate in retrospect the approximate maximum temperature reached in an unknown cooked meat sample by reference to a standard curve of soluble nitrogen versus known heat treatment.