On the response of ballistic soap to one-dimensional shock loading

The effects of projectile penetration into soft tissue are often studied using the tissue simulant ballistic soap. Consequently, a full understanding of the high strain-rate response of ballistic soap is desirable. Using the plate-impact technique, key shock parameters have been measured for impacts in the range 81–968 m/s, allowing derivation of the Hugoniot equation-of-state for soap in the U_S–u_P and σ_X–u_P planes. A polynomial Hugoniot relationship was found in the U_S–u_P plane, with the general form U_S = 1.96 + 2.41u_P − 0.72u_P² (ρ₀ = 1.107 g/cc). Further, embedded lateral manganin stress gauges were employed to interrogate the evolution of lateral stress within the soap. A gradient in lateral stress, whose magnitude increased incrementally with impact stress, was apparent behind the shock for σ_X >1 GPa. It is proposed that at higher values of σ_X, increased compression of hydrocarbon chains acts to increase the materials resistance to shear, a phenomenon consistent with steric hindrance.     

The design of mosaic armour: The influence of tile size on ballistic performance

Silicon carbide square tiles of different areal geometries and manufactured via two different processing routes have been bonded to polycarbonate layers to evaluate their ballistic performance. Four ceramic tile sizes were tested: 85 mm, 60 mm, 50 mm and 33 mm. In each case the residual depth-of-penetration into a polycarbonate semi-infinite backing was recorded. To elucidate the penetration and failure mechanisms, a computational model using the JH-1 ceramic model [Holmquist TJ, Johnson GR. Response of silicon carbide to high velocity impact. J Appl Phys 2002;91:5858–66] of the projectile used in the experimental study penetrating into a silicon carbide-faced polycarbonate was implemented in the hydrocode AUTODYN-2D. This paper shows that there is a critical dimension of tile that should be used in a silicon carbide-based ceramic-faced mosaic armour system design to ensure optimum system performance when each tile is struck centrally.     

Shock behaviour of a phenolic resin

Phenolic resins are used in many aspects of everyday life, e.g. as the matrix material for carbon fibre laminates used in the aerospace industry. Consequently, detailed knowledge of this material, especially while under shock loading, is extremely useful for the design of components that could be subjected to impact during their lifespan. The shock Hugoniot equations of state for phenolic resin (Durite SC-1008), with initial density of 1.18 g cm⁻³ have been determined using the plate-impact technique with in situ manganin stress gauges. The Hugoniot equation in the shock velocity–particle velocity plane was found to be non-linear in nature with the following equation: U _S = 2.14 + 3.79u _p − 1.68u _p². Further, the Hugoniot in the pressure–volume plane was observed to largely follow the hydrostatic curve. Lateral gauge measurements were also obtained. An ANSYS Autodyn^TM 2D model was used to investigate the lateral stress behaviour of the SC-1008. A comparison of the Hugoniot elastic limit calculated from the shear strength and measured sound speeds gave reasonable agreement with a value of 0.66 ± 0.35 GPa obtained.     

The effect of varying barrier height on the operationalcharacteristics of 1.3-μm strained-layer MQW lasers

This paper presents an empirical study of the effects that barrier layer composition has on the operational characteristics of 1.3-μm-wavelength InGaAsP-InP multiquantum-well (MQW) strained-layer ridge-waveguide lasers. A systematic empirical investigation of how this design choice affects practical device operation was undertaken by examining threshold current, efficiency, and modal gain as a function of temperature in five different laser structures. The results of these studies indicate that small barrier heights improve device performance, despite the loss of electronic confinement in the shallow conduction band quantum wells. Indeed, it appears that carrier uniformity in the MQW structure may be improved by carrier redistribution due to thermal or tunneling effects, which in turn enhances the operation of the low barrier height structures     

Regional activation of L-type voltage-sensitive calcium channels in experimental thiamine deficiency

At present (putative) human carcinogens are identified via epidemiological studies and testing using the chronic 2-yr rodent bioassay. Both methods have severe limitations in that they are slow, insensitive, expensive, and are also hampered by many uncertainties. The development of methods to modify specific genes in the mammalian genome has provided promising new tools for use in identifying carcinogens and characterizing their (qualitative) risk. Several transgenic mouse lines are currently under study to test their possible use in short-term carcinogenicity testing. One such candidate alternative transgenic model is the XPA knock-out mouse. These mice have an almost complete deficiency in DNA nucleotide excision repair (NER). Nevertheless, XPA-deficient mice are viable and have a background of a low incidence of spontaneous development of cancers. Approximately 15% of the mice develop hepatocellular adenomas (only after 1.5 yr). After treatment with ultraviolet-B radiation or 7,12-dimethylbenz(a)anthracene, the XPA-deficient mice developed squamous cell carcinomas and papillomas, respectively, on their skin. Oral treatment of XPA-deficient mice with benzo[a]pyrene (B[a]P), 2-acetylaminofluorene (2-AAF), and 2-amino-1-methyl-6-phenylimidazo [4,5-b]-pyridine (PhIP) resulted in lymphomas (B[a]P), liver and bladder tumors (2-AAF), and intestinal adenomas plus lymphomas (PhIP). These results look encouraging, but it should be noted that the compounds and agents tested thus far have all been substrate for nucleotide excision repair. Animal studies with different genotoxic or nongenotoxic compounds, as organized for instance within the framework of the International Life Sciences Institute/Health and Environmental Sciences Institute program, are needed to further evaluate the suitability of the XPA model for short-term carcinogenicity testing.     

A low rate of reinfection following effective therapy against Helicobacter pylori in a developing nation (China)

Ascorbate peroxidase (APX) is a hydrogen peroxide-scavenging peroxidase which uses ascorbate (AsA) as the specific electron donor. APX has not been isolated in mammals. Ocular tissue contains AsA at high concentrations, and we detected APX activity in bovine retinal pigment epithelium (RPE) and choroid. We purified APX from bovine RPE and choroid by four chromatographic steps. The purified APX was a monomeric hemoprotein with a molecular mass of 43 kDa. The amino acid sequence of the amino-terminal region of the purified APX showed a high degree of homology to that of plants. The primary product of the APX reaction was identified as the monodehydroascorbate radical. The APX showed high specificity for AsA as an electron donor. This is the first isolation and characterization of APX from mammals, and its role in the protection against active species of oxygen in ocular tissue is discussed.     

The use of an interactive computer program for the education of parents of asthmatic children

OBJECTIVES: To evaluate the effect of a single evening meal (gorging) on plasma lipids and lipoproteins in normal individuals observing the Ramadan Fast. During the Ramadan month, Muslims refrain from food and liquids during the day and eat a large meal after sundown. DESIGN: Sequential measurement of plasma lipids and lipoproteins in Muslims observing the Ramadan Fast and non-fasting individuals. SETTING: The study was conducted in the Bedouin town of Rahat, in the northern Negev area of Israel. SUBJECTS: Twenty-two healthy subjects who fasted during Ramadan and 16 non-fasting laboratory workers, were studied before Ramadan, at week 1, 2 and 4 of the Ramadan month, and again four weeks after the end of Ramadan. RESULTS: Plasma high-density lipoprotein cholesterol (HDL) rose significantly (P < 0.001) at the week 4 measurement, returning to basal levels 4 weeks after the end of Ramadan. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL), very-low density lipoprotein cholesterol (VLDL), and lipoprotein (a) [Lp(a)] did not change significantly. CONCLUSIONS: Plasma HDL increased by 23% after four weeks of gorging. The dietary change did not affect the composition of other lipoproteins, such as LDL, VLDL or Lp(a), other plasma biochemical parameters, or BMI. Prolonged gorging, well tolerated by all individuals, is a very effective non-pharmacological method to increase plasma HDL-cholesterol.     

Seroprevalence of HIV infection in childbearing women in Nova Scotia

The coupling of 2,3,6,2',3',4',6-hepta-O-acetyl-alpha-lactosyl bromide with 1,4-di-O-benzyl-D-threitol using mercury(II) cyanide as a promoter, with subsequent deprotection of one or both of the benzyl groups, further glycosylation, and deacetylation afforded the title compounds. This class of compound is useful in the assessment of binding properties of D-galactopyranose to human and rabbit hepatocytes.