Failure of the ERBE scanner instrument aboard NOAA 10 spacecraft and results of failure analysis

The Earth Radiation Budget Experiment (ERBE) scanner instrument on the NOAA 10 spacecraft malfunctioned on May 22, 1989, after more than 4 years of in-flight operation. After the failure, all instrument operational mode commands were tested and the resulting data analyzed. Details of the tests and analysis of output data are discussed therein. The radiometric and housekeeping data appear to be valid. However, the instrument will not correctly execute operational scan mode commands or the preprogrammed calibration sequences. The data indicate the problem is the result of a failure in the internal address decoding circuity in one of the ROM (read only memory) chips of the instrument computer

Impedance Eduction for Multisegment Liners

This paper explores the validity of an indirect method for impedance eduction of multisegment liners. This is accomplished via results obtained with two uniform liners and one two-segment liner, where each segment is constructed to match the geometry of one of the uniform liners. Each uniform liner is evaluated using direct and indirect impedance eduction methods. An indirect impedance eduction method is used to educe the impedance for each segment of the two-segment liner, and the results are compared with those educed for the uniform liners. These impedance spectra are shown to compare favorably for the majority of test conditions. Poorer comparisons are achieved for those test conditions where one segment of the two-segment liner provides little attenuation. Poor attenuation is a wellknown cause for impedance eduction difficulties. Overall, this multisegment impedance eduction method offers the potential to study complicated liners in a more efficient manner (i.e., without the requirement to build and test separate liners to duplicate each unique segment of the multisegment liner). More detailed studies are required to further validate this tool, and are intended to be the focus of future research

Evaluation of Variable-Depth Liner Configurations for Increased Broadband Noise Reduction

This paper explores the effects of variable-depth geometry on the amount of noise reduction that can be achieved with acoustic liners. Results for two variable-depth liners tested in the NASA Langley Grazing Flow Impedance Tube demonstrate significant broadband noise reduction. An impedance prediction model is combined with two propagation codes to predict corresponding sound pressure level profiles over the length of the Grazing Flow Impedance Tube. The comparison of measured and predicted sound pressure level profiles is sufficiently favorable to support use of these tools for investigation of a number of proposed variable-depth liner configurations. Predicted sound pressure level profiles for these proposed configurations reveal a number of interesting features. Liner orientation clearly affects the sound pressure level profile over the length of the liner, but the effect on the total attenuation is less pronounced. The axial extent of attenuation at an individual frequency continues well beyond the location where the liner depth is optimally tuned to the quarter-wavelength of that frequency. The sound pressure level profile is significantly affected by the way in which variable-depth segments are distributed over the length of the liner. Given the broadband noise reduction capability for these liner configurations, further development of impedance prediction models and propagation codes specifically tuned for this application is warranted

Variable-Depth Liner Evaluation Using Two NASA Flow Ducts

Four liners are investigated experimentally via tests in the NASA Langley Grazing Flow Impedance Tube. These include an axially-segmented liner and three liners that use reordering of the chambers. Chamber reordering is shown to have a strong effect on the axial sound pressure level profiles, but a limited effect on the overall attenuation. It is also shown that bent chambers can be used to reduce the liner depth with minimal effects on the attenuation. A numerical study is also conducted to explore the effects of a planar and three higher-order mode sources based on the NASA Langley Curved Duct Test Rig geometry. A four-segment liner is designed using the NASA Langley CDL code with a Python-based optimizer. Five additional liner designs, four with rearrangements of the first liner segments and one with a redistribution of the individual chambers, are evaluated for each of the four sources. The liner configuration affects the sound pressure level profile much more than the attenuation spectra for the planar and first two higher-order mode sources, but has a much larger effect on the SPL profiles and attenuation spectra for the last higher-order mode source. Overall, axially variable-depth liners offer the potential to provide improved fan noise reduction, regardless of whether the axially variable depths are achieved via a distributed array of chambers (depths vary from chamber to chamber) or a group of zones (groups of chambers for which the depth is constant)

From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways

The human body hosts an enormous abundance and diversity of microbes, which perform a range of essential and beneficial functions. Our appreciation of the importance of these microbial communities to many aspects of human physiology has grown dramatically in recent years. We know, for example, that animals raised in a germ-free environment exhibit substantially altered immune and metabolic function, while the disruption of commensal microbiota in humans is associated with the development of a growing number of diseases. Evidence is now emerging that, through interactions with the gut-brain axis, the bidirectional communication system between the central nervous system and the gastrointestinal tract, the gut microbiome can also influence neural development, cognition and behaviour, with recent evidence that changes in behaviour alter gut microbiota composition, while modifications of the microbiome can induce depressive-like behaviours. Although an association between enteropathy and certain psychiatric conditions has long been recognized, it now appears that gut microbes represent direct mediators of psychopathology. Here, we examine roles of gut microbiome in shaping brain development and neurological function, and the mechanisms by which it can contribute to mental illness. Further, we discuss how the insight provided by this new and exciting field of research can inform care and provide a basis for the design of novel, microbiota-targeted, therapies.GB Rogers, DJ Keating, RL Young, M-L Wong, J Licinio, and S Wesseling

Removal of organic material from recycle nitric acid by ozone

Organic compounds can be removed from recycle nitric acid (e.g., 2.5 to 10 M HNO/sub 3/) by ozonation. In the absence of catalysts the removal of acetic acid, one of the most resistant of the aliphatic species, was found to be slower than its removal from distilled water under similar conditions. At 95/sup 0/C, about 8 h was required to reduce the carbon content of a 10 M HNO/sub 3/ solution from 100 to 10 ..mu..g/m1 in the absence of catalysts. However, the same reduction was accomplished in only about 1 h when silver ion was added at a concentration of 50 mg/liter. Silver ion (Ag/sup +/) is the nmost effective of the catalysts tested for removal of acetic acid from 2.5 to 10 M HNO/sub 3/ by ozonation. Other, less efficient, catalysts include Pd/sup 2 +/, Mn/sup 2 +/, Fe/sup 3 +/, and silica gel. The initial stages of the reaction in nitric acid appear to be first order with respect to the acetic acid conentration when no catalyst is present. Average rate constants are 1.75 x 10/sup -5/ s/sup -1/ at 75/sup 0/C, 4.50 x 10/sup -5/ s/sup -1/ at 85/sup 0/C, and 1.02 x 10/sup -4/ s at 95/sup 0/C. The pseudo activaion energy calculated from an Arrhenius plot of these data is about 27 kcal/mole

Synthesis of aliphatic nitrate esters by reaction of metal nitrates with phosphate esters

A safe and simple method of synthesizing short-chain alkyl nitrates is described. This method, which should be of general utility, was found to be useful in preparing compounds for studies to determine the fate of organic materials in nuclear fuel reprocessing operations. Nitrate esters of short-chain alkyl alcohols can be conveniently obtained by distilling mixtures of the appropriate trialkyl phosphate with metallic nitrate salts. Runaway reactions are avoided by using only those metal nitrates that initially undergo an endothermic reaction with trialkyl phosphate. The nitrates of lithium, iron(III), and uranium among others, meet this criterion; lithium nitrate was found to be the most convenient. The purity of the product is more dependent on the temperature used and the purity of the nitrate salt than on the specific metal present in the salt. Details of the synthesis of n-butyl nitrate are given as an example of the method