Evaluation of the propensity of replacements for halon 1301 to induce stress-corrosion cracking in alloys used in aircraft fire-suppressant storage and distribution systems

The fire-suppressant agents halon 1301 and halon 1211 have both been determined to possess sufficient ozone layer depletion potential to warrant strict limitations on their production and use. The service conditions aboard jet aircraft subject engine fire-suppressant storage vessels to the agents for long durations at elevated temperatures and pressures. Stress-corrosion cracking (SCC) of the materials of the vessel wall and/or rupture disk assembly (agent release valve) could prevent proper operation. Therefore, the compatibility of potential replacements with the materials used in the fire-suppressant storage and distribution systems is a serious concern. An evaluation of the relative SCC propensity of 12 halon replacement candidates was conducted to enable the selection of three of these compounds for further study. The slow-strain-rate (SSR) tensile test was selected, and a statistical method was developed for ranking the relative susceptibility of each alloy in each agent from the SSR test results. The results revealed that most agents had little tendency to cause SCC, but that some agent/alloy combinations were undesirable. The statistical technique allowed relative comparison, ranking, and combination of these results with other types of tests for the identification of three agents suitable for development and evaluation as aircraft fire suppressants.     

Mathematical Models for Communication: An Introduction

In the situation where man is deprived of all possibility of intellectualization, that is, of interpreting geometrically a given process, either he will seek to create, despite everything, through suitable interpretations, an intuitive justification of the process, or he will sink into resigned incomprehension which habit will change to indifference…. The dilemma posed all scientific explanation is this: magic or geometry? (Thom, 1975, p. 5)     

Dielectric properties of YNi2B2C

The dielectric function of the quarternary superconductor YNi₂B₂C has been derived in an energy range from WmeV up to 50eV by linking together optical reflectance and electron energy loss measurements, obtained from polycrystalline samples at room temperature. The low energy part of the spectrum was additionally investigated in a temperature range from 10K up to 300K. In order to determine the anisotropy of this compound, the reflectance spectra of a single crystal were taken, using polarized light with polarization along the crystallographic axes. The single crystal data exhibit a normal Drude-like metallic behaviour, while the polycrystalline data can only be interpreted by means of a strong energy dependent scattering rate, which has been interpreted as resulting from strong electron-phonon coupling.     

Reasons for the different classification of structural steels according to their transition temperatures under different test conditions

Examples for the different classification of two steels under two test conditions if the curves transition temperature versus grain size intersect. Coherence of these curves with the curves for the temperature dependence of the Hall-Petch parameters σ_i, and k_y and with the value of a fracture parameter k_f. Technical significance of the results.     

Feasibility of using CO2 snow for refrigerating railcars shipping frozen foods

Six transport test runs have been carried out with insulated railcars containing frozen foods cooled with an initial charge of liquid CO₂ instead of using a mechanical refrigerating unit driven by a diesel engine. The test results have shown that a CO₂ cooling system is feasible, both from the economical and technical viewpoints.     

Susceptibility of cloned K+ channels to reactive oxygen species

Free radical-induced oxidant stress has been implicated in a number of physiological and pathophysiological states including ischemia and reperfusion-induced dysrhythmia in the heart, apoptosis of T lymphocytes, phagocytosis, and neurodegeneration. We have studied the effects of oxidant stress on the native K+ channel from T lymphocytes and on K+ channels cloned from cardiac, brain, and T-lymphocyte cells and expressed in Xenopus oocytes. The activity of three Shaker K+ channels (Kv1.3, Kv1.4, and Kv1.5), one Shaw channel (Kv3.4), and one inward rectifier K+ channel (IRK3) was drastically inhibited by photoactivation of rose bengal, a classical generator of reactive oxygen species. Other channel types (such as Shaker K+ channel Kv1.2, Shab channels Kv2.1 and Kv2.2, Shal channel Kv4.1, inward rectifiers IRK1 and ROMK1, and hIsK) were completely resistant to this treatment. On the other hand tert-butyl hydroperoxide, another generator of reactive oxygen species, removed the fast inactivation processes of Kv1.4 and Kv3.4 but did not alter other channels. Xanthine/xanthine oxidase system had no effect on all channels studied. Thus, we show that different types of K+ channels are differently modified by reactive oxygen species, an observation that might be of importance in disease states.     

THEORY AND COMPUTATION OF THE CHARACTERISTICS OF THE THERMAL ELECTRIC PLASMA ARC FOR CHEMICAL ENGINEERING APPLICATIONS

A generalized mathematical model has been developed for calculation of the characteristics of a thermal plasma arc under convective conditions. The geometry of the system analyzed is based on a novel technique which has demonstrated the capability of having a stream of gas injected into the core of the arc column around a cathode electrode with a high degree of penetration without affecting the arc stability allowing high throughputs of material. The general problem of the simultaneous solution of the conservation equations of mass, momentum, energy, and charge for a continuous plasma had been shown using incremental iterative techniques. High throughput convective arcs will now make practical many chemical and physical transformation processes. The inclusion of a more comprehensive current density makes the thermal arc more characterized than heretofore.     

Ether lipid derivatives: Antineoplastic activity in vitro and the structure-activity relationship

The antineoplastic activity of two ether lipid derivatives, the alkyl-lysophospholipid derivative (ALP) ET-18-OCH₃ and the ether-linked lipoidal amine CP-46,665 was tested in a human tumor clonogenic assay (HTCA) in vitro. CP-46,665 suppresed the colony formation of various human tumors with a slight dose response relation after 1 hr incubation and with a clear optimum (85% response rate) after continuous exposure in the higher dose range tested (10 μg/ml). ET-18-0CH₃ did not have substantial activity after 1 hr of incubation. However, when continuous exposure to the compound was used, ET-18-OCH₃ seemed to have a modest dose response effect and yielded a response in about 60% of the tumor cell samples tested in the higher dose range (10 μg/ml). Thus, both compounds have in vitro antitumor activity in the HTCA within a dose range of 1–10 μg/ml, especially during continuous exposure. The tumor specific type activity was found in breast cancer, ovarian cancer, lung cancer and mesothelioma. Both compounds caused decreases in colony formation down to the 0%, 2% and 4% levels. In a comparison of specimens in which both compounds were used, only one of five times showed a discordance in sensitivity or resistance; therefore the compounds appear similar in their in vitro activity. In a second set of experiments we tested the structure-activity relationship among a variety of ALP in the [³H]thymidine incorporation assay after incubation with HL-60 leukemic blasts and other neoplastic cells from human origin. From these studies it can be concluded that in the ALP the alkyl linkage in the sn-1 position is a necessary prerequisite for cytotoxicity; furthermore, in the majority of tumors tested the substitution of the sn-2 position to prevent reacylation of the molecule is necessary for cytotoxicity.     

Enhanced analysis of poly(ethylene glycols) and peptides using thermospray mass spectrometry

The effects of a needle-tip repeller electrode on thermospray mass spectra of poly(ethylene glycols) and peptide samples have been studied. A significant increase in ion current was observed for increased repeller potentials in the low-mass region (m/z 300 to m/z 1100) and the high-mass region (m/z 1100 to m/z 1900). The change in ion current is due to a change in ion extraction efficiency because of increased ion diffusion rates. The amount of peptide sample needed for direct injection studies was decreased 1 to 2 orders of magnitude by using an ion source with both a needle-tip repeller electrode and a restricted vaporizer probe tip.