The effect of annealing on the variation of glass refractive index.

The variation of refractive index (RI) over a non-toughened, float pane of glass and a toughened, float pane of glass was investigated. The two panes of colourless, float glass were cut into 150 5 cm × 5 cm squares. The pre- and post-annealing RI values from three random areas from each square were measured. Bayesian statistical hierarchical modelling of the results showed that for the non-toughened, float glass pane annealing increased the variability in RI by a factor of 1.29-1.58, with a mean of 1.43 (with 95% probability); and for the toughened, float pane of glass annealing decreased the variability in RI by a factor of 0.63-0.76, with a mean of 0.69 (with 95% probability). In addition it was found that although there were no systematic differences in ΔRI across either pane of glass, there were observable differences across both panes of glass. These results provide information regarding the expected RI variation over entire panes of both non-toughened and toughened float window glass for both pre- and post-annealing RI measurements.

Spatial variation of refractive index in a pane of float glass.

In the statistical interpretation of forensic glass evidence it is standard practice to make the assumption of homogeneity of the refractive index (RI) of the source glass, or of localized homogeneity. However, the work of Locke and Hayes showed that, for toughened windscreen glass, this assumption might not be true. This work is well cited, but there appears to have been little follow-on published research. Furthermore, the toughening process is something known to affect the refractive index, and is a process that float glass does not undergo. Float glass is a major component of casework in New Zealand and for that reason it would be interesting to know whether the findings of Locke and Hayes apply when dealing with float glass. In this paper we describe an experiment similar to that of Locke and Hayes, systematically examining the variation of RI in a pane of float window glass. It was found that, although there were no systematic differences in refractive index, there were observable differences across the pane.

How many samples from a drug seizure need to be analyzed?

Recently Aitken introduced an outstanding advance in the approach to decision making regarding drugs sampling. Unfortunately this approach has not, as yet, been widely implemented despite being based on a solid mathematical foundation. In this paper we advocate a Bayesian approach along the lines of that outlined by Aitken but designed to be both easily understood with less mathematical sophistication and implementable using standard EXCEL software. The emphasis is placed on encouraging the application of this methodology to routine case work by explaining the statistics involved. Minor differences exist between this approach and that of Aitken in both the modeling of the prior probability and in dealing with the discrete nature of the samples. These differences in no way detract from the sound mathematical foundation of the approach.

Glass on clothing and shoes of members of the general population and people suspected of breaking crimes.

The outer clothing and footwear of 122 people attending a university gymnasium and a private gymnasium were searched for fragments of glass. Both the surfaces and the pockets of the clothing and the uppers and soles of the footwear were searched. New Zealand forensic glass cases have been reviewed to determine the amount of non-matching glass present on the clothing of people who are suspected of breaking crimes. Data from 114 suspects who had no matching glass on their clothing and shoes were accumulated. Statistical modelling techniques have been applied to the data collected.

The effect of compressed air foam on the detection of hydrocarbon fuels in fire debris samples.

In 1998/99 the New Zealand Fire Service implemented compressed air foam delivery systems for the suppression of fires in rural areas. This study investigated whether the introduction of the foam to the seat of the fire created any problems in subsequent analyses of fire debris samples. No significant interferences from the foam were found when the samples were analysed by direct headspace using activated carbon strips. The only foam component detected was limonene.

The transfer of petrol on to clothing and shoes while pouring petrol around a room.

This study was aimed at measuring the approximate amount of petrol transferred on to the clothing and shoes of a person during the action of pouring petrol around a room. Two different heights of pouring and two different types of floor surface (carpet and concrete) were investigated. Results show that for all the combinations examined petrol was always transferred to the shoes and often transferred to the upper and lower clothing. This information illustrates the necessity of analysing the clothing and particularly the shoes of any suspected arsonists for the presence of hydrocarbon fuels.

Biological and immunoactive substances resembling chorionic gonadotropin are present in full-term horse and zebra placentas.

This study describes the presence of immunoactive and bioactive eCG-like material in full-term placentas of both domestic horses and zebras. Term placental extracts were immunoreactive in an LH monoclonal antibody RIA, and methods successfully used previously for the purification of eCG and eLH were employed to further concentrate the immunoreactive materials to the point where additional characterization studies could be performed. Sufficient equine material was obtained to perform a final fractionation on a concanavalin A Sepharose column yielding an unadsorbed fraction, e17A, and an adsorbed fraction, e17B. There was insufficient zebra material, z5D, for this step. HPLC gel filtration coupled with LH immunoassays of the column eluates showed all the final placental fractions to be highly heterogeneous, but a discrete peak of immunoactivity was found in one of the two equine fractions (e17B) and in the zebra fraction (z5D). The HPLC gel filtration elution volumes for e17B and z5D suggest that they have a smaller molecular size than either eCG or eLH but almost the same size as ovine LH. Both e17B and z5D were bioactive in the rat Leydig cell assay for LH but low in potency compared to eCG or eLH; e17A was inactive at very high doses (5 micrograms). This latter fraction, however, cross-reacted in an eCG alpha RIA to a much greater extent (6 times) than e17B, suggesting that it may be an incompletely formed or degraded alpha subunit. RIAs for LH, eCG, and eCG beta suggest that epitopes distinctive for these molecules are also present or similar to those in the term placental materials.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial purification and characterization of rhinoceros gonadotropins, growth hormone, and prolactin: comparison with the horse and sheep.

The rhinoceros is an endangered species related to the horse family. Little is known of its reproductive endocrinology. The objectives of this study were to partially purify rhinoceros pituitary hormones, determine which assays could be used for their assessment, and to ascertain whether rhinoceros LH possesses the intrinsic FSH activity of equine LH. A single pituitary each from a White (1.3 g) and a Black (1.2 g) Rhinoceros was homogenized and extracted (pH 9.5), then subjected to pH and salt fractionation, and ion-exchange chromatography (DEAE and Sephadex SP-C50) to yield partially purified fractions of LH, FSH, growth hormone (GH), and prolactin (PRL). LH was readily measured by a rat Leydig cell assay (0.1-1% x equine LH) and an RIA using a monoclonal antibody to bovine LH (6-11% x equine LH). FSH activity detected in the LH by either an FSH RIA or a calf testis radioreceptor assay (RRA) was extremely low. No FSH activity could be detected in the White Rhinoceros pituitary "FSH" fraction, but was readily detected in the Black Rhinoceros fraction (RIA: 0.2% x equine FSH: RRA: 0.8% x equine FSH). The presence of GH and PRL was determined by SDS-PAGE and Western blots. Results showed a single immunoreactive GH band and multiple immunoreactive PRL bands. Adsorption with Concanavalin A-Sepharose indicated that some of the PRL bands are glycosylated.