Prompt Shock Initiation of Cased Explosives by Projectile Impact

Experimental results often show that a prompt shock response to projectile impact can be experienced by even relatively heavily cased explosives. This paper will discuss the predictive criteria that can be applied in such circumstances, and in particular will explore the different mechanisms which are present for rod and sphere impacts. Predicted initiation thresholds are shown to give good comparisons with experimental results, using, at most, two empirical shock sensitivity constants obtained from impacts of the uncased explosive.     

A critical evaluation of indentation crack lengths in air

An extensive overview is presented of Vickers indentation crack lengths in ceramics in air. Measurement of such crack lengths is one of the most common and powerful assessments of the fracture properties of ceramics and the overview provides a critical evaluation of observed behavior as functions of material type and indentation load, and an extensive basis for comparison of results from new materials and analyses. The overview considers single crystals, polycrystals, transforming materials, glasses, and multiphase materials, including cermets, glass-ceramics, and tooth enamel. The coverage extends over structural and electronic ceramics, including oxides, carbides, nitrides, and titanates. The data are presented in a single format for ease of interpretation in terms of idealized indentation fracture and for inter-material comparisons; most data are unique to this work, but the results of selected studies from the published literature are included. The overview considers the precision and accuracy of crack length measurements and demonstrates a simple quantitative evaluation and ranking scheme for ceramic fracture based on load-adjusted crack length and cracking susceptibility. Indentation hardness and cracking threshold are also determined and related to the susceptibility. Material toughness is related to cracking susceptibility by fracture mechanics analyses: typical crack length measurements in air are shown to provide estimates of inert toughness with a relative uncertainty of ±50%.     

The impact of maturation on concentrations of key odour active compounds which determine the aroma of tequila

Samples of non‐mature and añejo (matured) tequila of the same brand/provenance were analysed using GC–MS and gas chromatography olfactometry (GC‐O)/aroma extract dilution analysis (AEDA) to provide quantitative data on the most odour active compounds that contribute to the aroma of these spirits. Extracts of non‐mature tequila were characterized by 26 odour‐active regions, which included ethyl hexanoate, ethyl octanoate, 2‐phenylethyl acetate, β‐damascenone, isoamyl alcohol and octanoic acid as the most odour‐active compounds (flavour dilution, FD, factor ≥ 6561). In contrast, extracts of the mature spirit showed 36 odour‐active zones, where the compounds with the highest FD factors (6561) were ethyl hexanoate, ethyl octanoate, 2‐phenylethyl acetate, isoamyl alcohol, phenethyl alcohol, guaiacol, 4‐ethyl guaiacol, vanillin, cis/trans whisky lactones, β‐damascenone and octanoic acid. The aromagram of mature tequila was thus differentiated from that of the non‐mature spirit owing to the presence of cask‐extractive compounds and the increased FD factors of certain terpenes, higher alcohols and acetals. This study provides a comprehensive and quantitative understanding of changes in key odourants of tequila as a result of the maturation process and also reveals a further characterization of the likely impact of each compound on overall spirit flavour, in terms of odour activity values. Copyright © 2016 The Institute of Brewing & Distilling     

Mechanisms of Ice Crystallization in Ice Cream Production

ABSTRACT: The smoothness and perceived quality of an ice cream depends in large part on the small size of ice crystals in the product. Understanding the mechanisms responsible for producing the disc‐shaped crystals found in ice cream will greatly aid manufacturers in predicting how processing and formulation changes will affect their product. Because ice cream mix is opaque, it has not yet been possible to observe ice crystallization in ice cream in situ. Studies to date, therefore, have used analogues or have related observed effects to a hypothesized mechanism. Still, some elements of the crystallization mechanism are well accepted. Because of the large supercooling at the freezer wall, ice nucleates there before being swept into the bulk of the freezer. In the bulk, heat and mass transfer cause some crystals to melt and others to grow. By the time the ice cream reaches the freezer exit, the ice crystals have become small, rounded discs.     

Salmonella in uncooked retail meats in New Zealand

A national quantitative survey of Salmonella in five types of uncooked retail meats in New Zealand was undertaken from August 2003 to May 2005 to establish baseline proportionality data. The overall prevalence of Salmonella in 1,108 meat samples was 1.1% (95% confidence interval, 0.6 to 1.9). Low prevalences of Salmonella in each meat type were observed, with 3% (1.2 to 6.1) in chicken, 1.3% (0.3 to 3.8) in lamb and mutton, 0.5% (0 to 3.0) in unweaned veal, 0.4% (0 to 2.4) in beef, and 0% (0 to 1.6) in pork. The Salmonella serotypes isolated were Salmonella Infantis from beef; Salmonella Typhimurium PT1 from unweaned veal and chicken; Salmonella sp. 6,7:k:-, Salmonella Enteritidis PT9a, Salmonella sp. 4,5,12:-:-, Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT160 from chicken; and Salmonella sp. 4:-:2 and Salmonella Brandenburg from lamb. Four of the isolates from chicken, Salmonella sp. 4,5,12:-:- (two isolates), Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT1, were very similar phenotypically and serologically to the attenuated Salmonella vaccine strain used in MeganVacl for poultry. One lamb sample yielded a count of Salmonella Brandenburg of 4.24 most probable number (MPN)/g, while all other positive samples were <1.0 MPN/g. The results provide baseline proportionality data for Salmonella in retail uncooked meats that will contribute invaluably toward future risk assessment in light of other information, such as consumption data that can be used for risk characterization.     

An improved HPLC method for single‐run analysis of the spectrum of hop bittering compounds usually encountered in beers

A single‐run reverse phase‐high performance liquid chromatography method for the quantification of humulinones, α‐acids, iso‐α‐acids and reduced iso‐α‐acids (where present) in commercial beer samples is presented. The method utilizes a binary solvent system consisting of (A) 1% v/v acetic acid and (B) 0.1% v/v orthophosphoric acid in acetonitrile. Separation was achieved on a Purospher® star RP‐18 column (250 × 46 mm, 3 µm) with a flow rate of 0.5 mL/min. The compounds of interest eluted within 32 min. The method was fully validated according to International Conference on Harmonization guidelines and subsequently applied to monitor degradation of hop acids in a storage trial where four lager beers were aged at 28 and 38 °C for 70 and 60 days, respectively. Results confirmed the widely reported degradation through storage of trans‐iso‐α‐acids whilst demonstrating that the HLPC method was sufficiently sensitive to monitor and model this degradation. One beer exhibited a significantly lower (P < 0.05) rate of trans‐iso‐α‐acid degradation than the other conventionally hopped beers in the study, which might have been linked to its higher pH (4.71 vs 4.36). The relative stability of reduced iso‐α‐acids during ageing was also confirmed.     

Reinvestigation of the antioxidant properties of conjugated linoleic acid

Despite repeated suggestions that antioxidant activity of conjugated linoleic acid (CLA), a collective of conjugated dienoic isomers of linoleic acid, underlies its reported anticarcinogenic and antiatherosclerotic effects, the antioxidant properties of CLA remain ill-defined. Therefore, this study was undertaken to gain more insight into the mechanism of potential CLA antioxidant activity. It was tested whether CLA could protect membranes composed of 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC) from oxidative modification under conditions of metal ion-dependent or-independent oxidative stress. Progress of oxidation was determined by direct spectrophotometric measurement of conjugated diene formation and by gas chromatographic/mass spectrometric analysis of fatty acids. The oxidative susceptibility of CLA was higher than that of linoleic acid, and comparable to arachidonic acid. When oxidation of PLPC (1.0 mM) was initiated using the lipid-soluble 2,2′-azobis(2,4-dimethylvaleronitrile) or the water-soluble 2,2′-azobis(2-amidinopropane) hydrochloride, the radical scavengers vitamin E and butylated hydroxytoluene (BHT) at 0.75 μM efficiently inhibited PLPC oxidation, as evident from a clear lagphase. In contrast, 0.75 μM CLA did not have any significant effect on PLPC oxidation. Inhibition of PLPC oxidation by higher concentrations of CLA appeared due to competition, not to an antioxidant effect. When oxidation of PLPC was initiated by hydrogen peroxide/Fe²⁺ (500 μM/0.05–20 μM), both vitamin E (1 μM) and ethylene glycol-bis(aminoethyl ether) tetraacetic acid (50 μM) efficiently inhibited PLPC oxidation. However, CLA (1–50 μM) did not show a clear protective effect under any of the conditions tested. We conclude that CLA, under these test conditions, does not act as an efficient radical scavenger in any way comparable to vitamin E or BHT. CLA also does not appear to be converted into a metal chelator under metal-ion dependent oxidative stress, as had previously been suggested. On the basis of our observations, a role for CLA as an antioxidant does not seem plausible.     

Rheology, phase morphology, mechanical, impact and thermal properties of polypropylene/metallocene catalysed ethylene 1-octene copolymer blends

Blends of a polypropylene (PP) and a metallocene catalysed ethylene-octene copolymer (EOC) were prepared using a single screw extruder fitted with a barrier screw design. The EOC used had 25 wt% 1-octene content and the weight fraction of EOC in the blends covered the range 1-30 wt.% Viscosity values for the blends determined experimentally from dual capillary rheological studies were similar to those calculated theoretically using the log additivity principle described by Ferry. This result together with scanning electron microscopy (SEM) observations and evidence from tan δ curves from dynamic mechanical thermal analysis showed PP and EOC to be partially miscible for blends having 10 wt% EOC or less. The tensile modulus, break strength and flexural modulus of the blends decreased with respect to virgin PP as the weight fraction of EOC was increased to 30 wt.% The diminution in mechanical properties was concomitant with an initial increase in elongation at break from 40% for neat PP to 140% for the blend with 15 wt% EOC before decreasing to 65% when 30 wt% EOC was blended. The optimum impact modification of the PP used in this study, in the temperature range −40 to 23 °C, was achieved by blending with between 20 and 30 wt% EOC.     

Alumina Agglomerate Effects on Toughness-Curve Behavior of Alumina–Mullite Composites

Toughness-curve ( T -curve) behavior of composites of spherical, polycrystalline, coarse-grained, alumina agglomerates dispersed throughout a constant-toughness, fine-grained, 50–50 vol% alumina–mullite matrix has been evaluated as a function of agglomerate content for the range 15 to 45 vol%. T -curve behavior was evaluated using the indentation-strength method. Increasing alumina agglomerate content resulted in a progressive increase of large indentation load strengths with negligible change of plateau strength levels at small indentation loads. This behavior is consistent with underlying T -curves that rise to greater values and are shifted toward longer crack lengths with increasing agglomerate content, suggesting that both bridge spacing and bridge potency increase with increasing agglomerate content over the range tested. The proposed relationships between bridge spacing and agglomerate content, and bridge potency and agglomerate content, are rationalized in terms of residual stress considerations. The indentation-strength data also demonstrated that the composite containing the greatest alumina agglomerate content, 45 vol%, exhibited the greatest flaw tolerance.     

Gender and dietary fat affect α-tocopherol status in F344/N rats

For four weeks, groups of eight male and eight female F344/N rats were fed diets containing 15.5, 20, 30 or 40% of energy (en%) as fat. The fat was composed of corn oil and beef tallow with 9 en% from linoleate in all diets. Females had greater mean hepatic α-tocopherol levels, whereas males had greater plasma α-tocopherol and cholesterol concentrations. In males, the plasma ratio of α-tocopherol/cholesterol was significantly greater than in females (P<0.05). Plasma α-tocopherol increased with increasing en% fat (r=0.51,P<0.001) in both sexes, but dietary fat did not alter hepatic α-tocopherol levels. These results suggest that plasma α-tocopherol may serve as a biomarker of total dietary fat intake and that in F344/N rats gender differences affect α-tocopherol and cholesterol status.