Using 3D printing to fabricate realistic test projectiles for natural fragmentation from buried charges.

Buried charges such as improvised explosive devices continue to be one of the most lethal and hidden threats service members face. On detonation, ground debris near the blast area is accelerated towards service members as secondary fragmentation, consisting of sand, gravel and rocks. In order to mitigate injury, protective equipment can be worn, yet it is difficult to gather accurate data for engineering decisions when the standard test uses a fragment simulating projectile made from metal. It is difficult to test secondary fragmentation from ground debris due to the natural heterogeneity and variance of the material. A methodical and reproducible method of testing fragmentation damage from ground debris was developed to study and improve protective equipment against natural secondary fragmentation. We present herein the novel process of 3D-printing ballistic projectiles from silica sand, followed by launching with an air canon. Outlined within are the successes, challenges and proposed implementations of the technology. The 3D-printed sand projectiles achieved speeds over 170 m/s, resulting in measurable damage to single Kevlar sheets. Other flight parameters such as yaw and rotation were captured, resulting in observations about design and shape of the projectiles. It was found that one design performed better in terms of velocity, rotation and impact. The technology has the potential to disrupt the protective equipment sector by providing a controlled means of assessing natural fragmentation damage.

Evidence for flocculation in glacier-fed Lillooet Lake, British Columbia.

This study provides evidence of in situ flocculation in a glacier-fed freshwater lake. Direct observation of flocculated particles using microscopy provides the strongest evidence to establish that clastic suspended sediment in Lillooet Lake is flocculated. Flocs in Lillooet Lake exhibit a hierarchical size structure, with primary particles (<4 microm) joining to create microflocs (10-35 microm), and both primary particles and microflocs joining to create macroflocs (200-280 microm). In situ laser particle sizing reveals primary particles and microflocs dominate in the epilimnion, a zone susceptible to shear induced by wind or inflow and exhibiting the highest suspended sediment loads. Macroflocs dominate in the hypolimnion, a more quiescent zone and exhibiting the lowest suspended sediment loads. Flocculated particles are invisible to traditional methods of sediment analysis in glaciolacustrine settings. Flocculation is a plausible explanation for accelerated sedimentation of the clay-sized sediments known to dominate the size distribution of varves in other glacier-fed lakes.

Perceptual learning in humans: roles of preexposure schedule, feedback, and discrimination assay.

In three experiments, humans received preexposure to two compound flavours (AX and BX: saline-lemon and sucrose-lemon) that were presented either in an intermixed (e.g., AX, BX,...BX, AX,...) or a blocked (e.g., AX, AX,...BX, BX...) fashion. Subsequently, AX was paired with an unpleasant bitter taste, and the discriminability of AX and BX was assessed using the accuracy of same/different judgements and by the extent to which any learned dislike of AX generalized to BX. When participants received feedback about the accuracy of their same/different judgements during preexposure those given intermixed preexposure were more accurate in making these judgements during the test than those given blocked preexposure (Experiments 1 and 2A), however, there was no evidence of any learned dislike in these experiments. In Experiment 2B, in which participants did not receive feedback about the accuracy of their judgements, there was no effect of the preexposure regime on same/different judgements, but there was a learned dislike of AX, and this generalized less to BX in participants given intermixed than in those given blocked preexposure. The beneficial effects of intermixed preexposure are consistent with results from other species (chicks and rats), but the differences created by the presence or absence of feedback place constraints on the analysis of these effects.

Representational blending in human conditional learning: Implications for associative theory.

In two experiments, participants were presented with pictures of different foods (A, B, C, D, X,) and learned which combinations resulted in an allergic reaction in a fictitious patient, Mr X. In Problem 1, when A or B (but not C or D) was combined with food X an allergic reaction occurred, and when C or D (but not A or B) was combined with Y an allergic reaction occurred. In Experiment 1, participants also received Problem 2 in which A, B, C, and D interacted with foods V and W either in the same way as X and Y, respectively, or in a different way. Participants performed more proficiently in the former than in the latter condition. In Experiment 2, after training on Problem 1, participants judged whether or not novel combinations of foods (e.g., AB, CD, AD, CB) would cause an allergic reaction in Mr X. They were no more likely to indicate that AB or CD would cause an allergic reaction than AD or CB, but made their judgements more rapidly and with greater confidence on AB and CD trials than on AD and CB trials. These results (1) indicate that shared representations come to be addressed by the components of similar compounds (e.g., AX and BX) that have predicted the same outcome (an allergic reaction), and (2) are inconsistent with standard, associative theories of learning, but (3) are consistent with findings from nonhuman animals and with a connectionist interpretation of these findings.

The influence of the economic and social environment on deliberate self-harm and suicide: an ecological and person-based study.

BACKGROUND: Geographic variations in the incidence of deliberate self-harm (DSH) and suicide have been shown to be associated with area-based measures of socio-economic deprivation and social fragmentation. Previous studies have been subject to methodological limitations. None has investigated whether ecological associations are reflected in characteristics of individuals involved in suicidal behaviour. METHODS: DSH patients presenting to a general hospital between 1985 and 1995 and suicides (including open verdicts) from the same catchment area were studied. Mean annual rates of DSH and suicide by gender were calculated for electoral wards. The wards were amalgamated into 20 groups according to their ranking for socio-economic deprivation (Townsend) and social fragmentation scores. Associations of these variables with DSH and suicide rates were investigated. Characteristics of DSH patients living in ward groups with the highest and lowest socio-economic deprivation and social fragmentation scores were compared. RESULTS: Socio-economic deprivation was associated with DSH rates among males (r = 0.89) and females (r = 0.87). After controlling for social fragmentation the associations remained relatively strong, particularly in young males. Associations with social fragmentation in both genders (males, r = 0.83; females, r = 0.86) were attenuated after controlling for socio-economic deprivation. For suicide, the only significant association was with socio-economic deprivation in males (r = 0.79), but this was attenuated after controlling for social fragmentation. The characteristics of individual DSH patients reflected those of the areas where they lived. CONCLUSIONS: Reducing socio-economic deprivation and its associated problems may be an important strategy in the prevention of suicidal behaviour, especially in young men.

What in earth? Analysing soil bacterial communities.

Walk into any field and you will at once see dozens of plant and animal species. However, below your feet and largely unnoticed, lies a population of unseen millions. Can the introduction of powerful molecular biological techniques increase our understanding of how these hidden bacterial communities function in their natural environment?

Structure-activity relationships for induction of peroxisomal enzyme activities by phthalate monoesters in primary rat hepatocyte cultures.

Rat hepatocytes were cultured for 70 hours with a series of four isomeric octyl and five isomeric hexyl phthalate monoesters, and their effects on peroxisomal fatty acid beta-oxidation (palmitoyl-CoA oxidation) and carnitine acetyltransferase activities determined. All nine monoesters produced dose-related increases in enzyme activities and marked quantitative compound potency differences were observed. Generally octyl isomers were more potent than hexyl isomers and 2- and 3-ethyl substituted isomers were more potent than their straight chain and 1-ethyl substituted analogs. For example, mono(2-ethylhexyl)phthalate was more potent than mono(1-ethylhexyl)phthalate, and this was also observed after oral administration of the two isomers to rats for seven days. The cell culture data for induction of palmitoyl-CoA oxidation were used to generate quantitative structure-activity relationships. Relatively poor correlations were observed between biological activity and simple hydrophobic parameters, but a good correlation was obtained when compound electronic structural parameters, obtained by molecular orbital calculations, were employed. These studies demonstrate relationships between biological activity and chemical structure for a series of phthalate monoesters and indicate the potential usefulness of primary rat hepatocyte cultures to screen compounds for peroxisome proliferation.

Structure activity studies on the induction of peroxisomal enzyme activities by a series of phthalate monoesters in primary rat hepatocyte cultures.

A series of 9 phthalate monoesters were cultured with primary rat hepatocytes for 70 h and their effect on peroxisomal fatty acid beta-oxidation (palmitoyl-CoA oxidation) determined. Marked quantitative differences in the induction of enzyme activity were observed with both alkyl chain length and position of side chain substitution affecting compound potency. With all 9 compounds a good correlation was observed between electronic structural parameters obtained by molecular orbital calculations and biological activity in the cell culture system. These results demonstrate a relationship between chemical structure and biological activity for a series of phthalate monoesters and indicate the potential usefulness of primary hepatocyte cultures to screen compounds for peroxisome proliferation.

The effect of peroxisome proliferators on the metabolism and spectral interaction of endogenous substrates of cytochrome P-450 in rat hepatic microsomes.

The peroxisome proliferators clofibric acid and di-(2-ethylhexyl)-phthalate (DEHP) preferentially induced the 12-hydroxylation, compared to the 11-hydroxylation, of lauric acid in rat liver microsomes. A marked increase in the affinity of spectral interaction of this substrate with cytochrome P-450 was also observed. In addition, both clofibric acid and DEHP treatment produced a marked effect on the profile of site- and stereo-specific microsomal metabolites of testosterone. These results demonstrate that both peroxisome proliferators induce similar form(s) of cytochrome P-450 which are active in the metabolism of endogenous substrates of cytochrome P-450. The possible relevance of these findings to the hepatotoxicity of peroxisome proliferators is discussed.