Peroxy radical detection by chemical amplification (PERCA)

Important reactions of atmospheric free radicals are the chain oxidation of NO and CO. Thus: H2O + NO yields OH + NO2; OH + CO yields H + CO2; H + O2 + M yields HO2 + M. In most models, the need to know the free radical concentration could also be described as the need to know the rate of the above oxidation chain in the atmosphere. It is the total rate of this chain (also carried by RO2 and RO) which was measured using the PERCA. The PERCA is thus essentially a RO sub X meter. The PERCA works by adding excess CO (10%) and NO (5ppm) to a stream of air and measuring the NO2 produced after 3s of reaction time. Since other processes produce NO2, the chain reaction is modulated by switching the CO for N2. The chain length is limited by the reaction OH + NO yields HONO and is modeled to be somewhat over 1000. Measured chain lengths agree with the modeled numbers

Chemiluminescent measurement of atmospheric acid

The design and construction of a gas phase acid sensitive analyzer are reported. These studies showed that the chemical system was a practical analytical method. A complete instrument was developed and prepared for field testing. A Titan 3-C rocket was scheduled for launching on February 11, 1974. Through preparations made by NASA Langley the instrument was set up to monitor the acid concentration in the rocket exhaust. Due to adverse wind conditions no acid was detected. This entire trip is described in detail

Studying the Interaction : Remix Literacy in the Writing Classroom

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Direct measurement of diurnal polar motion by ring laser gyroscopes

We report the first direct measurements of the very small effect of forced diurnal polar motion, successfully observed on three of our large ring lasers, which now measure the instantaneous direction of Earth's rotation axis to a precision of 1 part in 10^8 when averaged over a time interval of several hours. Ring laser gyroscopes provide a new viable technique for directly and continuously measuring the position of the instantaneous rotation axis of the Earth and the amplitudes of the Oppolzer modes. In contrast, the space geodetic techniques (VLBI, SLR, GPS, etc.) contain no information about the position of the instantaneous axis of rotation of the Earth, but are sensitive to the complete transformation matrix between the Earth-fixed and inertial reference frame. Further improvements of gyroscopes will provide a powerful new tool for studying the Earth's interior.Comment: 5 pages, 4 figures, agu2001.cl

Development and validation of the child post-traumatic cognitions inventory (CPTCI)

Background: Negative trauma-related cognitions have been found to be a significant factor in the maintenance of post-traumatic stress disorder (PTSD) in adults. Initial studies of such appraisals in trauma-exposed children and adolescents suggest that this is an important line of research in youth, yet empirically validated measures for use with younger populations are lacking. A measure of negative trauma-related cognitions for use with children and adolescents, the Child Post-Traumatic Cognitions Inventory (CPTCI), is presented. The measure was devised as an age-appropriate version of the adult Post-Traumatic Cognitions Inventory (Foa et al., 1999). Methods: The CPTCI was developed and validated within a large (n = 570) sample, comprising community and trauma-exposed samples of children and adolescents aged 6-18 years. Results: Principal components analysis suggested a two-component structure. These components were labelled 'permanent and disturbing change' and 'fragile person in a scary world', and were each found to possess good internal consistency, test-retest reliability, convergent validity, and discriminative validity. The reliability and validity of these sub-scales was present regardless of whether the measure was completed in the acute phase or several months after a trauma. Scores on these sub-scales did not vary with age. Conclusions: The CPTCI is a reliable and valid measure that is not specific to the type of trauma exposure, and shows considerable promise as a research and clinical tool. The structure of this measure suggests that appraisals concerning the more abstract consequences of a trauma, as well as physical threat and vulnerability, are pertinent factors in trauma-exposed children and adolescents, even prepubescent children

Assessment of possible environmental effects of space shuttle operations

The potential of shuttle operations to contribute to atmospheric pollution is investigated. Presented in this interim report are results of the study to date on rocket exhaust inventory, exhaust interactions, dispersion of the ground cloud, detection and measurement of hydrochloric acid and aluminum oxide, environmental effects of hydrochloric acid and aluminum oxide, stratospheric effects of shuttle effluents, and mesospheric and ionospheric effects of orbiter reentry. The results indicate space shuttle operation will not result in adverse environmental effects if appropriate launch constraints are met

Hall state quantization in a rotating frame

We derive electromagnetomotive force fields for charged particles moving in a rotating Hall sample, satisfying a twofold U(1) gauge invariance principle. It is then argued that the phase coherence property of quantization of the line integral of total collective particle momentum into multiples of Planck's quantum of action is solely responsible for quantization in the Hall state. As a consequence, the height of the Hall quantization steps should remain invariant in a rapidly rotating Hall probe. Quantum Hall particle conductivities do not depend on charge and mass of the electron, and are quantized in units of the inverse of Planck's action quantum.Comment: 6 pages, accepted for publication in Europhysics Letter

Gravitomagnetism, clocks and geometry

New techniques to evaluate the clock effect using light are described. These are based on the flatness of the cylindrical surface containing the world lines of the rays constrained to move on circular trajectories about a spinning mass. The effect of the angular momentum of the source is manifested in the fact that inertial observers must be replaced by local non rotating observers. Starting from this an exact formula for circular trajectories is found. Numerical estimates for the Earth environment show that light would be a better probe than actual clocks to evidence the angular momentum influence. The advantages of light in connection with some principle experiments are shortly reviewed.Comment: TCI Latex, 12 pages, 2 figures. To appear in European Journal of Physic

Little groups of irreps of O(3), SO(3), and the infinite axial subgroups

Little groups are enumerated for the irreps and their components in any basis of O(3) and SO(3) up to rank 9, and for all irreps of C$_{\infty}$, C$_{\infty h}$, C$_{\infty v}$, D$_{\infty}$ and D$_{\infty h}$. The results are obtained by a new chain criterion, which distinguishes massive (rotationally inequivalent) irrep basis functions and allows for multiple branching paths, and are verified by inspection. These results are relevant to the determination of the symmetry of a material from its linear and nonlinear optical properties and to the choices of order parameters for symmetry breaking in liquid crystals.Comment: 28 pages and 3 figure