Evaluation of selected strapdown inertial instruments and pulse torque loops, volume 1

Design, operational and performance variations between ternary, binary and forced-binary pulse torque loops are presented. A fill-in binary loop which combines the constant power advantage of binary with the low sampling error of ternary is also discussed. The effects of different output-axis supports on the performance of a single-degree-of-freedom, floated gyroscope under a strapdown environment are illustrated. Three types of output-axis supports are discussed: pivot-dithered jewel, ball bearing and electromagnetic. A test evaluation on a Kearfott 2544 single-degree-of-freedom, strapdown gyroscope operating with a pulse torque loop, under constant rates and angular oscillatory inputs is described and the results presented. Contributions of the gyroscope's torque generator and the torque-to-balance electronics on scale factor variation with rate are illustrated for a SDF 18 IRIG Mod-B strapdown gyroscope operating with various pulse rebalance loops. Also discussed are methods of reducing this scale factor variation with rate by adjusting the tuning network which shunts the torque coil. A simplified analysis illustrating the principles of operation of the Teledyne two-degree-of-freedom, elastically-supported, tuned gyroscope and the results of a static and constant rate test evaluation of that instrument are presented

New Chemistry of Imidazolinium ylides

Previous work in this group has shown 4,5-dihydroimidazolium ylides, formed by N- alkylation of 4,5-dihydroimidazoles, to undergo 1,3-dipolar cycloadditions with a range of dipolarophiles in a highly regio- and stereoselective fashion. We have investigated two further aspects of this chemistry: (1) the synthesis of 4,5-dihydroimidazoles substituted with a heteroatom at C-2 and the subsequent N-alkylation of those templates followed by deprotonation to potentially access novel azomethine ylides; and (2) an intramolecular variant of the 1,3-dipolar cycloaddition, synthesising for this purpose a series of bromomethyl(co-l)-oxoalkenoates as dipolarophiles and subsequently reacting these with some 4,5-dihydroimidazole templates. The synthesis of 4,5-dihydroimidazoles substituted with a heteroatom at C-2 was developed from 1-enzyltetrahydroimidazol-2-thione 131. Methylation of this with either iodomethane or methyl trifluoromethanesulfonate provided a key methylthioimidazolium iodide intermediate 135 from which 2-alkanethio- (136), 2-alkoxy (137) and 2-dialkylamino- (138) 4,5-dihydroimidazoles could be prepared by deprotonation, reaction with an alkoxide or reaction with a dialkylamine, respectively. N-Alkylation of the heterocycles was found to be unsuccessful. An alternative strategy, involving the synthesis of l-benzyl-3-methoxycarbonylmethyltetrahydroimidazol-2-one 143a and -2-thione 143b, was developed. The oxygen-containing compound 143a was transformed into its corresponding 0-substituted salts by treatment with triethyloxonium tetrafluoroborate, trimethylsilyl trifluoromethanesulfonate or trifluoromethanesulfonic anhydride. The sulfur analogue 143b was S-methylated using methyl trifluoromethanesulfonate. However, neither of the salts was found to undergo a 1,3-dipolar cycloaddition reaction upon treatment with DBU followed by methyl acrylate. Intramolecular 1,3-dipolar cycloaddition reactions of a variety of ɑ-bromoketones with 1- benzyl4,5-dihydroimidazoles proved successful. Thus, reaction of 1-benzyl-4,5- dihydroimidazole 29 with methyl E-8-bromo-7-oxooct-2-enoate 196a followed by treatment with DBU afforded the tricyclic pyrroloquinoxaline adducts methyl 1-benzyl-2,3,7,8,9,9a-hexahydro-1H-pyrrolo[1,2,3-de]quinoxaline-6-carboxylate 217. This arises from the primary cycloadduct undergoing a cascade involving an eliminative ring-opening, recyclisation, loss of water and prototropic shift cascade. Seven other examples of this reaction, involving 2- and 4-phenyl-4,5-dihydroimidazoles, and ethyl and tertbutyl E-8-bromo-7-oxooct-2-enoate, as well as with 2- and 3-methyl substituted octenoates (i.e trisubstituted double bonds). In these cases no cycloaddition reaction involving the double bond occurs. In one instance, the reaction of (R)-4-phenyl-4,5-dihydroimidazole 112 with tert-butyl E-8-bromo-7-oxooct-2-enoate 278, we were able to isolate the primary cycloadduct, tert-butyl (3R,4aR,8aS,9S,9aR)-1-benzyl-5-oxo-3-phenyldecahydro-1H-imidazo[1,2-ɑ] indole-9-carboxylate 283. It would appear that the combination of sterically demanding phenyl and tert-butyl groups precludes eliminative ring-opening

Road verge vegetation and the capture of particulate matter air pollution

Urban air quality is considered a major issue in cities worldwide, with particulate matter (PM) recognised as one of the most harmful pollutants regarding human health. The use of plants to act as air filters and immobilise PM has been identified as a potential method to improve the air quality in these areas. The majority of the work has focused on trees, with the application of shrub and herbaceous species largely overlooked. Two contrasting leaf morphologies from a shrub and herbaceous plant species were sampled at four locations across Southampton (UK), from varying traffic conditions. Samples were analysed for the mass of PM captured, particle size, and elemental composition. These analyses were used to characterise the different sites and the plants’ effectiveness at immobilisation of PM. Captured PM mass was shown to be directly related to traffic density, with greater traffic density leading to higher levels of captured PM. PM origins were attributed to emissions from vehicles and the resuspension of particles by vehicle movement. The bulk of the PM mass was shown to originate from natural, crustal sources including large proportions of Al, Si, and/or Ca. Increases in elements from anthropogenic enhancement (such as Fe and Zn) were related to high traffic density. Particle size analysis identified that, despite the use of standard leaf-washing protocols with a final 2.5 µm filter, PM was dominated by fine particles (<2.5 µm physical diameter), with particles >10 µm rare. Bramble leaves were calculated to have a species-specific deposition velocity 0.51 cm s−1 greater than ivy, with deposition velocities calculated at 1.8 and 1.3 cm s−1 for ivy and 2.3 and 1.8 cm s−1 for bramble at Redbridge Road and Brinton’s Road, respectively. These values can allow for the more accurate modelling and estimation of the PM removal abilities of these plants

Synthesis of some new 2-heterosubstituted 4,5-dihydroimidazoles

Several new 4,5-dihydroimidazoles (and the corresponding imidazolium salts) carrying heteroatom substituents at C-2 have been prepared from the corresponding tetrahydroimidazol-2-ones and/or -thiones

Limits on Relief through Constrained Exchange on Random Graphs

Agents are represented by nodes on a random graph (e.g., small world or truncated power law). Each agent is endowed with a zero-mean random value that may be either positive or negative. All agents attempt to find relief, i.e., to reduce the magnitude of that initial value, to zero if possible, through exchanges. The exchange occurs only between agents that are linked, a constraint that turns out to dominate the results. The exchange process continues until a Pareto equilibrium is achieved. Only 40%-90% of the agents achieved relief on small world graphs with mean degree between 2 and 40. Even fewer agents achieved relief on scale-free like graphs with a truncated power law degree distribution. The rate at which relief grew with increasing degree was slow, only at most logarithmic for all of the graphs considered; viewed in reverse, relief is resilient to the removal of links.Comment: 8 pages, 2 figures, 22 references Changes include name change for Lory A. Ellebracht (formerly Cooperstock, e-mail address stays the same), elimination of contractions and additional references. We also note that our results are less surprising in view of other work now cite

Agricultural Phosphorus Management and Water Quality Protection in the Midwest

For nutrient management planners -- to understand the risk of phosphorus in surface waters and to manage this risk. Targeted for Iowa, Kansas, Missouri, and Nebraska.https://lib.dr.iastate.edu/extension_ag_pubs/1151/thumbnail.jp

Maternal deaths in Pakistan : intersection of gender, class and social exclusion.

Background: A key aim of countries with high maternal mortality rates is to increase availability of competent maternal health care during pregnancy and childbirth. Yet, despite significant investment, countries with the highest burdens have not reduced their rates to the expected levels. We argue, taking Pakistan as a case study, that improving physical availability of services is necessary but not sufficient for reducing maternal mortality because gender inequities interact with caste and poverty to socially exclude certain groups of women from health services that are otherwise physically available. Methods: Using a critical ethnographic approach, two case studies of women who died during childbirth were pieced together from information gathered during the first six months of fieldwork in a village in Northern Punjab, Pakistan. Findings: Shida did not receive the necessary medical care because her heavily indebted family could not afford it. Zainab, a victim of domestic violence, did not receive any medical care because her martial family could not afford it, nor did they think she deserved it. Both women belonged to lower caste households, which are materially poor households and socially constructed as inferior. Conclusions: The stories of Shida and Zainab illustrate how a rigidly structured caste hierarchy, the gendered devaluing of females, and the reinforced lack of control that many impoverished women experience conspire to keep women from lifesaving health services that are physically available and should be at their disposal