The reactions of aliphatic nitroso compounds.

Thesis (M.A.)--Boston UniversityThis research was undertaken to test the action of various oxidizing agents on two typical aliphatic nitroso compounds, propyl pseudonitrole and N-nitrosodimethylamine. The oxidizing agents tested include benzoyl peroxide, acetyl peroxide, 30% hydrogen peroxide, urea peroxide, potassium ferricyanide, and nitric acid. To test the reaction with pseudonitrole it was necessary to dissolve that compound in various solvents including carbon tetrachloride, ethyl acetate, and glacial acetic acid. With the N-nitrosodimethylamine it was found possible to dissolve the peroxides in the amine itself. The N-nitroso compound was not tested with potassium ferricyanide or nitric acid. [TRUNCATED

Improved Artificial Viscosity in Finite Element Method (FEM) for Hypervelocity Impact Calculations

AbstractIn this paper we develop methods based primarily on the work of Kuropatenko and Wilkins to improve the application of artificial viscosity in 3D finite element method (FEM) codes. The primary goal is to obtain better shock predictions for hypervelocity impacts (HVI) and reduce the need for user calibration. We focus on examining factors such as geometric variability with respect to shock direction, dynamic adaptation to changes in compressibility in the shock front, and anisotropic compression in multi-dimensional formulations. We implement the methods in the Velodyne hydro-structural code and investigate the effects on shock propagation using a series of simple flyer impact test cases which cover a range of system responses including strong and weak shocks. Various initial mesh geometries are utilized to examine mesh effects. Energetic materials using the Ignition and Growth Reactive Burn (IGRB) equation of state (EOS) are also examined due to the rapid change in compressibility and energy density which occurs due to reaction. These rapid changes can lead to insufficient damping in artificial viscosity calculations and thus provide an effective test case. We employ the CTH hydrocode to evaluate baseline shock behavior. The regular, ordered mesh of CTH allows for a consistent and precise application of the artificial viscosity. Direct numerical comparisons are used rather than experimental data to eliminate uncertainty due to factors such as material characterizations, EOS models, and mesh resolution. We compare the CTH results against various FEM artificial viscosity implementations to evaluate performance. It is demonstrated that shock response in FEM codes can be significantly improved by using updated artificial viscosity methods

Identifying Farmers\u27 Interest in Growing Switchgrass for Bioenergy in Southern Virginia

Several factors are generating interest in growing switchgrass for energy. To understand farmers\u27 perspectives on possible switchgrass cultivation, Cooperative Extension conducted a survey in south-central and southwestern Virginia. The survey found that 66% of respondents had heard of using switchgrass for bioenergy, yet only 43% indicated they would be interested in cultivating switchgrass even if the enterprise were profitable. Reluctance to consider growing a potentially profitable crop is likely due to an underdeveloped market and lack of familiarity with switchgrass culture. The results indicate an important role for Extension in conveying technical information to producers as biofuel markets develop

Life insurance portfolio management

Based on the institutional and economic environment in which life insurance companies operate, this study develops a theoretical portfolio model with sufficient empirical content to yield hypotheses about life insurance portfolio behavior which are readily tested with appropriate econometric techniques. State quantitative and qualitative restrictions on portfolio composition, the accounting procedures promulgated by the National Association of Insurance Commissioners, Federal tax laws, and other taxes and regulations provide the institutional setting for the life insurance investment process. Given these, the solvency of a life insurance company is affected by the riskiness of its investment portfolio, the uncertainty of future operating expenses, and the uncertainty of cash flows between the policyholder and the company. This study focuses on the first of these sources of risk and abstracts away from the other two. A simple chance-constrained model is presented which integrates the basic economic variables relevant to life insurance company portfolio management. In this model, the firm's objective is to maximize its rate of return on its portfolio subject to a probabalistic solvency constraint, legal constraints, a balance sheet constraint, and non-negativity constraints. Given parameters for the model, the optimal portfolio may be specified, and a sensitivity analysis to parameter changes provides the basis for several testable hypotheses. Several significant economic relationships were found using an econometric analysis of a cross-sectional/time series panel of 92 large U.S. life insurance companies over the 1957-71 time period. The amount of surplus and a proxy for the level of financial yields were positively related to investments in equities and negatively related to investments in bonds and mortgages. Company size was positively related to the proportion of assets invested in common stock and bonds and inversely related to the proportional investment in mortgages. Distributed lag models showed the response to changes in independent variables to be fairly rapid, with the demand for bonds and common stock possessing the highest adjustment rates and changes in the amount of surplus causing the most rapid responses. While New York regulated companies generally invest in less common stock, this result is largely explained by the economic differences between New York licensed companies and other companies. Stock companies invested in more conservative portfolios than mutuals, given the independent variables: this result is expected because of the differences in the life insurance products sold by the two types of firms. Considerable unexplained interfirm variation persisted, perhaps because the high substitutability among financial assets makes prediction difficult. Relative yields often did not prove to be significant determinants of portfolio choices. These results may be due to the problems of multi collinearity, autocorrelation, and sample size, but the poor performance of yields may have other bases, as well. In the chance constrained model, the demand for a security is a complex function and, conceptually, the demand for a security may be inversely related to its own yield. The demand for a security will be inelastic with respect to yield changes when upper or lower bound constraints are binding. In addition, the normative significance of relative yields may be questionable if yield changes occur in response to other characteristics of securities such as maturity, liquidity, and risk of default when these other features are not explicitly accounted for in the model. This study of life insurance portfolio behavior deals with, a number of important theoretical and empirical problems. While the empirical results generally conform to expectations derived from an analytical model, much portfolio variation remains unexplained. At the same time, however, much portfolio variation among the large life insurance companies in this study does appear to have a rational economic basis.Economics, Department o

Laser-Induced Plasma Analysis for Surrogate Nuclear Debris

This work identifies analytical lines in laser-induced plasma for chemical analyses of major elements found in surrogate nuclear debris. These lines are evaluated for interferences and signal strength to insure they would be useful to measure relative concentrations. Compact, portable instruments are employed and can be included as part of a mobile nuclear forensics laboratory for field screening of nuclear debris and contamination. The average plasma temperature is measured using the well-established Boltzmann plot technique, and plasma\u27s average electron density is determined using empirical formulae based on Stark broadening of the H-alpha line. These measurements suggest existence of partial local thermal equilibrium

Positive impact of pre-stroke surgery on survival following transient focal ischemia in hypertensive rats

We describe a positive influence of pre-stroke surgery on recovery and survival in a commonly used experimental stroke model. Two groups of male, stroke-prone spontaneously hypertensive rats (SHRSPs) underwent transient middle cerebral artery occlusion (tMCAO). Group 1 underwent the procedure without any prior intervention whilst group 2 had an additional general anaesthetic 6 days prior to tMCAO for a cranial burrhole and durotomy. Post-stroke recovery was assessed using a 32 point neurological deficit score and tapered beam walk and infarct volume determined from haematoxylin–eosin stained sections. In group 2 survival was 92% (n = 12) versus 67% in group 1 (n = 18). In addition, post-tMCAO associated weight loss was significantly reduced in group 2. There was no significant difference between the two groups in experimental outcomes: infarct volume (Group 1 317 ± 18.6 mm<sup>3</sup> versus Group 2 332 ± 20.4 mm<sup>3</sup>), and serial (day 0–14 post-tMCAO) neurological deficit scores and tapered-beam walk test. Drilling a cranial burrhole under general anaesthesia prior to tMCAO in SHRSP reduced mortality and gave rise to infarct volumes and neurological deficits similar to those recorded in surviving Group 1 animals. This methodological refinement has significant implications for animal welfare and group sizes required for intervention studies

Connectionist natural language parsing

The key developments of two decades of connectionist parsing are reviewed. Connectionist parsers are assessed according to their ability to learn to represent syntactic structures from examples automatically, without being presented with symbolic grammar rules. This review also considers the extent to which connectionist parsers offer computational models of human sentence processing and provide plausible accounts of psycholinguistic data. In considering these issues, special attention is paid to the level of realism, the nature of the modularity, and the type of processing that is to be found in a wide range of parsers

Reassessment of the risk of narcolepsy in children in England 8 years after receipt of the AS03-adjuvanted H1N1 pandemic vaccine: A case-coverage study.

BACKGROUND: Early studies of narcolepsy after AS03-adjuvanted pandemic A/H1N12009 vaccine (Pandemrix) could not define the duration of elevated risk post-vaccination nor the risk in children aged under 5 years who may not present until much older. METHODS/FINDINGS: Clinical information and sleep test results, extracted from hospital notes at 3 large pediatric sleep centers in England between September 2017 and June 2018 for narcolepsy cases aged 4-19 years with symptom onset since January 2009, were reviewed by an expert panel to confirm the diagnosis. Vaccination histories were independently obtained from general practitioners (GPs). The odds of vaccination in narcolepsy cases compared with the age-matched English population was calculated after adjustment for clinical conditions that were indications for vaccination. GP questionnaires were returned for 242 of the 244 children with confirmed narcolepsy. Of these 5 were under 5 years, 118 were 5-11 years, and 119 were 12-19 years old at diagnosis; 39 were vaccinated with Pandemrix before onset. The odds ratio (OR) for onset at any time after vaccination was 1.94 (95% confidence interval [CI] 1.30-2.89), The elevated risk period was restricted to onsets within 12 months of vaccination (OR 6.65 [3.44-12.85]) and was highest within the first 6 months. After one year, ORs were not significantly different from 1 up to 8 years after vaccination. The ORs were similar in under five-year-olds and older ages. The estimated attributable risk was 1 in 34,500 doses. Our study is limited by including cases from only 3 sleep centers, who may differ from cases diagnosed in nonparticipating centers, and by imprecision in defining the centers' catchment population. The potential for biased recall of onset shortly after vaccination in cases aware of the association cannot be excluded. CONCLUSIONS: In this study, we found that vaccine-attributable cases have onset of narcolepsy within 12 months of Pandemrix vaccination. The attributable risk is higher than previously estimated in England because of identification of vaccine-attributable cases with late diagnoses. Absence of a compensatory drop in risk 1-8 years after vaccination suggests that Pandemrix does not trigger onsets in those in whom narcolepsy would have occurred later

Ultrasensitive force and displacement detection using trapped ions

The ability to detect extremely small forces is vital for a variety of disciplines including precision spin-resonance imaging, microscopy, and tests of fundamental physical phenomena. Current force-detection sensitivity limits have surpassed 1 $aN/\sqrt{Hz}$ (atto $=10^{-18}$) through coupling of micro or nanofabricated mechanical resonators to a variety of physical systems including single-electron transistors, superconducting microwave cavities, and individual spins. These experiments have allowed for probing studies of a variety of phenomena, but sensitivity requirements are ever-increasing as new regimes of physical interactions are considered. Here we show that trapped atomic ions are exquisitely sensitive force detectors, with a measured sensitivity more than three orders of magnitude better than existing reports. We demonstrate detection of forces as small as 174 $yN$ (yocto $=10^{-24}$), with a sensitivity 390$\pm150$ $yN/\sqrt{Hz}$ using crystals of $n=60$ $^{9}$Be$^{+}$ ions in a Penning trap. Our technique is based on the excitation of normal motional modes in an ion trap by externally applied electric fields, detection via and phase-coherent Doppler velocimetry, which allows for the discrimination of ion motion with amplitudes on the scale of nanometers. These experimental results and extracted force-detection sensitivities in the single-ion limit validate proposals suggesting that trapped atomic ions are capable of detecting of forces with sensitivity approaching 1 $yN/\sqrt{Hz}$. We anticipate that this demonstration will be strongly motivational for the development of a new class of deployable trapped-ion-based sensors, and will permit scientists to access new regimes in materials science.Comment: Expanded introduction and analysis. Methods section added. Subject to press embarg