Isomerization as a Key Path to Molecular Products in the Gas-Phase Decomposition of Halons

The decomposition of halons remains controversial concerning the branching between radical and molecular products. The latter channel, where it has been found, is presumed to occur via a constrained symmetric multicenter transition state. Isomerization pathways in the gas-phase chemistry of halons have rarely been considered, despite the fact that the iso-halons, which feature a halogen−halogen bond, are widely recognized as important reactive intermediates in condensed phases. In this Letter, detailed calculations and modeling of the unimolecular decomposition of several important halons, including CF2Cl2, CF2Br2, and CHBr3, reveal that isomerization is a key pathway to molecular products. This path is important for both halons and their primary radicals as the barrier to isomerization in these compounds is typically isoenergetic with the threshold for bond fission

Pathways to Equity: An Auto-Ethnographic and Narrative Study of Teacher Educator and Preservice Teachers in a One-Credit Course and Community-Based Field Experience

the student population in the United States within the next several years, while predominately White teachers will continue to compromise the teaching population. Schools continually fail to serve racially, culturally, and linguistically diverse students, particularly African American students. As such, a critical issue within teacher education is how to best prepare teachers to teach across the lines of ethnicity/race, language, and social class. In response to this issue, this study looked closely at the identities, perspectives, and experiences of a teacher educator and undergraduate, preservice teachers throughout a one-credit education course infused with elements of equity pedagogies and an added community-based field experience. Using autoethnographic and narrative methodologies, this study sought to explore self-narratives as pathways to helping teacher educators and preservice teachers begin to recognize the need to work toward equity in education. Findings of this study reflect complexities within the identities and socialization processes of a teacher educator and preservice teachers, providing insights for promoting the growth of a sociocultural consciousness required for teaching equity pedagogies. Findings indicate that the teacher educator and preservice teachers were strongly socialized to a view of Whiteness as normalized and, while most preservice teachers gained insights from the course and were able to counter deficit-laden assumptions of children and their families as a result of their course experiences, there were considerable challenges involved in the process which included: examining the normalization of Whiteness, colorblind and racist dispositions, and the use of deflection strategies (deflecting from a focus on deficit perspectives of children and their families). Implications are provided to shed light on what this might mean in terms of equity in literacy education, especially suggestions for supporting preservice teachers and teacher educators in recognizing inequities and making commitments toward changing an unjust society

Dynamics of Race, Culture and Key Indicators of Health in the Nation's 100 Largest Cities and Their Suburbs

Profiles the 2000 status of, and changes since 1990, in rates of health and health-related measures to identify patterns in race/ethnicity, foreign-born status, language use, poverty, income, low birth weight, teen births, prenatal care, and tuberculosis

A Comparative Study of Self Esteem As it Relates to Alcohol Use Among Inmates with Learning Disabilities and Inmates With No Prior Special Education Services.

The purpose of this study was to examine the relationship between learning disabilities and self esteem as it relates to alcohol use in young men at a correctional facility. A standardized alcohol questionnaire was distributed to those men identified as having a learning disability and to nondisabled men. Subjects were matched according to age and sex. Those students who were identified as having a learning disabilitity had a specially coded survey for identification purposes. Names did not appear on the questionnaire in order to maintain strict confidentiality. Those men who were receiving learning disabilities services were found to have a higher correlation between low self esteem and alcohol consumption than those men who had never received special education services

Spectroscopic and Computational Studies of Matrix-Isolated iso-CXBr3 (X=F,Cl,Br): Structure, Properties, and Photochemistry of Substituted Iso-Tribromomethanes

Iso-polyhalomethanes are important reactive intermediates in the condensed and gas-phase chemistry of halomethanes. Building upon our recent study of iso-bromoform, in this work the substituted iso-tribromomethanes (iso-CXBr3; X = F, Cl, Br) were characterized by matrix isolation infrared and UV/Vis spectroscopy, supported by ab initio calculations, to further probe the structure, spectroscopy, properties, and photochemistry of these important intermediates. Selected wavelength laser irradiation of CXBr3 samples in an inert rare gas (typically Ar; mixing ratio 1:500) held at ∼5 K yielded iso-CXBr3 (XBrC–Br–Br or Br2C–Br–X). The observed infrared and UV/Vis absorptions are in excellent agreement with computational predictions, and the energies of various stationary points on the CXBr3 Potential Energy Surfaces (PESs) were characterized computationally using DFT, MP2, and CCSD (T) methods in combination with triple-zeta quality basis sets. These calculations show that the isomers are minima on the PESs that lie ∼200 kJ/mol above the global CXBr3 minimum, yet are bound by some 50–70 kJ/mol in the gas-phase with respect to the CXBr2 + Br asymptote. Laser irradiation of the isomers resulted in back photoisomerization to CXBr3, and intrinsic reaction coordinate (IRC) calculations confirmed the existence of a first order saddle point connecting the two isomers. Calculations of important stationary points on the CXBr3 PESs show that in the gas-phase the isomerization barrier lies energetically near the threshold for simple bond fission. The iso-CXBr3 species are significantly stabilized in the condensed phase, due to the high degree of ion-pair character, as revealed by Natural Resonance Theory analysis

Depth-Based Signal Separation with Vertical Line Arrays in the Deep Ocean

Deep vertical line arrays can exploit the reliable acoustic path (RAP), which provides low transmission loss (TL) for targets at moderate ranges, and increased TL for distant interferers. However, nearby surface interference also has favorable RAP propagation and cannot be separated from a submerged target without horizontal aperture. In this work, a physics-based Fourier transform variant is introduced, which achieves depth-based signal separation by exploiting the spatial structure resulting from the coherent addition of the direct and surface-reflected propagation paths present for submerged sources. Simulation results demonstrate depth-based signal separation without requiring knowledge of the ocean environment

Probing Radical Pathways in Electrophilic Addition of Halogens: Classical vs. Bridged Intermediates

We examine radical mediated pathways in electrophilic addition to the simplest alkene, ethylene, where the structure of the radical intermediate has been extensively debated. Starting from the π-complex with a dihalogen, C2H4⋯I2, isolated in an inert matrix, we initiate reaction by photolytically cleaving the I2 bond. We succeed in trapping and spectroscopically interrogating the symmetrically bridged radical complex, which calculations confirm is the global minimum on the C2H5I Potential Energy Surface (PES). Consistent with the participation of a bridged intermediate, radical addition preferentially but not exclusively yields the anti-stereoisomer of the 1,2-diiodoethane product

On the Electronic Spectroscopy of the Iso-Polyhalomethanes

The iso-polyhalomethanes are important reactive intermediates, displaying intense near-UV absorption bands that have been assigned to the S0 → S3 transition on the basis of Time-Dependent Density Functional Theory (TDDFT) calculations. In this work, theory and multi-dimensional Franck–Condon (FC) analysis are used to model the electronic spectra of selected iso-polyhalomethanes. The S0 → S3 transition approximately corresponds to a π–π∗ transition on the halocarbocation subunit, which induces significant geometry changes. The calculated multimode FC profiles capture features of the experimental spectra of the matrix-isolated species, and are compared with the results of previous Resonance Raman studies of the isomers in solution

THE DIFFERENCES IN SPINAL KINEMATICS AND LOADING IN HIGH PERFORMANCE FEMALE ROWERS DURING ERGOMETER AND ON WATER ROWING

Low back pain (LBP) is the most prevalent injury in rowing. The high use of ergometers have been associated win increased LBP and sliding ergometers has proposed to reduce this stress. The purpose of this study was to examine the lumbar flexion angles on fixed and sliding ergometers versus on water conditions. Four elite female adult rowers volunteered for this study and completed a 1,000 meter maximal test on the stationary and fixed ergometers and then on water. Lumbar curvature (% flexion) was calculated) for the first 0.47 s following the catch position. Standardized mean differences (effect size) were calculated to examine differences in %ROM over time for each condition and between conditions. Results found that fixed rowers ergometers induced the greatest amount if lumbar flexion, with some reduction for sliding ergometers compared to on water