The 250-kW CW klystron amplifier for planetary radar

The design, construction, and performance testing is described of two Varian klystrons, model VKX-7864A, which replaced the aging and less efficient VA-949J klystrons in the X band planetary radar transmitter on the Goldstone, CA, 70 meter antenna. The project was carried out jointly by the JPL and Varian Assoc. Output power was increased from 200 to 250 kW continuous wave per klystron, and full dc beam power is dissipated in the collector (it was not possible to operate the VA-949J klystrons without RF drive because of limited collector dissipation capability). Replacements were made with a minimum of transmitter modifications. The planetary radar transmitter is now operating successfully with these two klystrons

A study to determine the extent of instruction of individual income taxes to bookkeeping students in the secondary schools of New England

Thesis (Ed.M.)--Boston Universit

Modeling the physical properties in the ISM of the low-metallicity galaxy NGC4214

We present a model for the interstellar medium of NGC4214 with the objective to probe the physical conditions in the two main star-forming regions and their connection with the star formation activity of the galaxy. We used the spectral synthesis code Cloudy to model an HII region and the associated photodissociation region (PDR) to reproduce the emission of mid- and far-infrared fine-structure cooling lines from the Spitzer and Herschel space telescopes for these two regions. Input parameters of the model, such as elemental abundances and star formation history, are guided by earlier studies of the galaxy, and we investigated the effect of the mode in which star formation takes place (bursty or continuous) on the line emission. Furthermore, we tested the effect of adding pressure support with magnetic fields and turbulence on the line predictions. We find that this model can satisfactorily predict (within a factor of ~2) all observed lines that originate from the ionized medium ([SIV] 10.5um, [NeIII] 15.6um, [SIII] 18.7um, [SIII] 33.5um, and [OIII] 88um), with the exception of [NeII] 12.8um and [NII] 122um, which may arise from a lower ionization medium. In the PDR, the [OI] 63um, [OI] 145um, and [CII] 157um lines are matched within a factor of ~5 and work better when weak pressure support is added to the thermal pressure or when the PDR clouds are placed farther away from the HII regions and have covering factors lower than unity. Our models of the HII region agree with different evolutionary stages found in previous studies, with a more evolved, diffuse central region, and a younger, more compact southern region. However, the local PDR conditions are averaged out on the 175 pc scales that we probe and do not reflect differences observed in the star formation properties of the two regions.Comment: accepted for publication in A&

Interference effects in two-photon ATI by multiple orders high harmonics with random or locked phases

We numerically study 2-photon processes using a set of harmonics from a Ti:Sapphire laser and in particular interference effects in the Above Threshold Ionization spectra. We compare the situation where the harmonic phases are assumed locked to the case where they have a random distribution. Suggestions for possible experiments, using realistic parameters are discussed.Comment: 11 pages, 13 figures, LaTe

Coulomb-Volkov approach of ionization by extreme ultraviolet laser pulses in the subfemtosecond regime

In conditions where the interaction betweeen an atom and a short high-frequency extreme ultraviolet laser pulse is a perturbation, we show that a simple theoretical approach, based on Coulomb-Volkov-type states, can make reliable predictions for ionization. To avoid any additional approximation, we consider here a standard case : the ionization of hydrogen atoms initially in their ground state. For any field parameter, we show that the method provides accurate energy spectra of ejected electrons, including many above threshold ionization peaks, as long as the two following conditions are simultaneously fulfilled : (i) the photon energy is greater than or equal to the ionization potential ; (ii) the ionization process is not saturated. Thus, ionization of atoms or molecules by the high order harmonic laser pulses which are generated at present may be addressed through this Coulomb-Volkov treatment.Comment: 19 pages including 5 figures and figure caption

Statistical and cartographic modeling of vernal pool locations: Incorporating the spatial component into ecological modeling

Vernal pools are small, isolated, depressions that experience cyclical periods of inundation and drying. Many species have evolved strategies to utilize the unique characteristics of vernal pools; however, their small size, seasonal nature, and isolation from other, larger water bodies, suggest increased risk of damage/loss by development. The goals of this research were to statistically determine physical predictors of vernal pool presence and, subsequently, to represent the output cartographically for use as a conservation tool. Logistic regression and Classification and Regression Tree (CART) routines were used to define important variables (slope, aspect, land use, soils, and reflectance) of 405 known vernal pools across northeastern Massachusetts. The CART models performed most favorably, achieving cartographic accuracies as high as 97% and providing a set of rules for vernal pool prediction. This combined statistical and spatial approach represents an efficient and accurate method of identifying vernal pools in Massachusetts and other, similar landscapes

The Conflict Tactics Scale: Assessing the meaning, context, and consequences of partner violence.

The purpose of the present study was to test if the Conflict Tactics Scale (CTS) is a valid measure of the incidence/prevalence of partner violence and whether it overestimates the comparability of male and female victimization. Similar to other studies using the CTS, 36% of females and 52% of males reported being victimized by either a current or past partner. Significantly more females (55%) than males (34%) reported perpetrating an act from the CTS. Responses on the CTS would therefore suggest that females are more violent than males and that males suffer more abuse, but the supplementary information concerning the meaning, context, and consequences of violence provided by participants suggests that these conclusions are not warranted. Male and female experiences as victims of violence differ dramatically. A considerable proportion of female victims of violence described patterns of abuse in which their partner started the confrontation, was the sole aggressor, was responsible for the altercation, and who acted out of frustration, anger, or desire to intimidate. Women reported suffering severe emotional trauma and in some cases, physical harm. Male victims of abuse provided information about their experiences which were full of contradictions. For example, while many men reporting victimization said that their partners started the violence, many of the same men indicated that their partners\u27 motive was retaliation of self-defense, suggesting a very different picture of abuse. Moreover, men reported little emotional and physical harm as a result of their victimization. (Abstract shortened by UMI.)Dept. of Psychology. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1995 .C675. Source: Masters Abstracts International, Volume: 34-06, page: 2496. Adviser: Charlene Senn. Thesis (M.A.)--University of Windsor (Canada), 1995

Copper oxide nanoparticles induce oxidative stress and cytotoxicity in airway epithelial cells

Metal oxide nanoparticles are often used as industrial catalysts and elevated levels of these particles have been clearly demonstrated at sites surrounding factories. To date, limited toxicity data on metal oxide nanoparticles are available. To understand the impact of these airborne pollutants on the respiratory system, airway epithelial (HEp-2) cells were exposed to increasing doses of silicon oxide (SiO2), ferric oxide (Fe2O3) and copper oxide (CuO) nanoparticles, the leading metal oxides found in ambient air surrounding factories. CuO induced the greatest amount of cytotoxicity in a dose-dependent manner; while even high doses (400 μg/cm2) of SiO2 and Fe2O3 were non-toxic to HEp-2 cells. Although all metal oxide nanoparticles were able to generate ROS in HEp-2 cells, CuO was better able to overwhelm antioxidant defenses (e.g. catalase and glutathione reductase). A significant increase in the level of 8-isoprostanes and in the ratio of GSSG to total glutathione in cells exposed to CuO suggested that ROS generated by CuO induced oxidative stress in HEp-2 cells. Co-treatment of cells with CuO and the antioxidant resveratrol increased cell viability suggesting that oxidative stress may be the cause of the cytotoxic effect of CuO. These studies demonstrated that there is a high degree of variability in the cytotoxic effects of metal oxides, that this variability is not due to the solubility of the transition metal, and that this variability appears to involve sustained oxidative stress possibly due to redox cycling. © 2009 Elsevier Ltd. All rights reserved

Photo-electron momentum spectra from minimal volumes: the time-dependent surface flux method

The time-dependent surface flux (t-SURFF) method is introduced for computing of strong-field infrared photo-ionization spectra of atoms by numerically solving the time-dependent Schr\"odinger equation on minimal simulation volumes. The volumes only need to accommodate the electron quiver motion and the relevant range of the atomic binding potential. Spectra are computed from the electron flux through a surface, beyond which the outgoing flux is absorbed by infinite range exterior complex scaling (irECS). Highly accurate infrared photo-electron spectra are calculated in single active electron approximation and compared to literature results. Detailed numerical evidence for performance and accuracy is given. Extensions to multi-electron systems and double ionization are discussed.Comment: 18 pages, 5 figure