Towards an understanding of the carbon isotopic changes across the Toarcian oceanic anoxic event

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005.Includes bibliographical references (p. 63-68).A combination of bulk carbon, biomarker and compound specific isotopic analyses were used in order to investigate the changes which accompanied the deposition of black shales during the upper tenuicostatum and lower falciferum zones of the Toarcian (early Jurassic, 183 Ma) ocean anoxic event (OAE). In this study, we reveal that apparent negative isotopic excursions in bulk organic and carbonate carbon were the result of compositional changes of organic matter and diagenesis, respectively. Organic petrology and Rock-Eval pyrolysis of organic matter from the Jet Rock, Hawsker Bottoms, Yorkshire, England, show that the upper tenuicostatum zone contains very large amounts of terrigenous debris. A careful review of the carbonate carbon record, as reported in the literature, indicates that a large negative isotopic excursion in bulk carbonate is likely the result of diagenesis, rather than reflective of seawater isotopic conditions. Biomarker distributions and isotopic composition of primary production biomarkers show little variation during the largest changes in the bulk records. Biomarker source indicators vary little throughout the section, indicating little change in biota or redox structure of the water column during this widespread deposition of black shales. Isotopic compositions of algal short chain n-alkanes, pristane and phytane also remain steady across the section.(cont.) Long chain n-alkanes, biornarkers for higher plants, also do not change during the event. Isorenieratane, a biomarker for green sulphur bacteria and an indicator of photic zone euxinia, however, show a strong peak in concentration coincident with the maximum abundance of organic carbon. Because we have found no evidence for significant isotopic variation on land or in the ocean, we must infer that there were no major redistributions of carbon in the ocean-atmosphere system during the Toarcian OAE. Therefore, oceanic overturn or large input of methane are not plausible explanations for this event. This deposition of black shales was a result of periodic episodic euxinia, which resulted in the increased preservation of organic matter. We believe that this event was not a large, one-time occurrence, but a characteristic response to paleogeography and oceanic circulation patterns of the Mesozoic.by Alison Margaret Cohen.S.M

Civil Rights Act of 1964 - Title VII - Sex Discrimination - Pregnancy - Defenses

The United States Court of Appeals for the Ninth Circuit has held that an airline\u27s employment policy mandating immediate unpaid maternity leave for all flight attendants upon discovery of pregnancy is sex discrimination but is justified by safety considerations. Harriss v. Pan American World Airways, Inc., 649 F.2d 670 (9th Cir. 1980)

The Nature of Hypervelocity Stars and the Time between Their Formation and Ejection

We obtain Keck HIRES spectroscopy of HVS5, one of the fastest unbound stars in the Milky Way halo. We show that HVS5 is a 3.62 ± 0.11 M_☉ main-sequence B star at a distance of 50 ± 5 kpc. The difference between its age and its flight time from the Galactic center is 105 ± 18 (stat) ±30 (sys) Myr; flight times from locations elsewhere in the Galactic disk are similar. This 10^8 yr "arrival time" between formation and ejection is difficult to reconcile with any ejection scenario involving massive stars that live for only 10^7 yr. For comparison, we derive arrival times of 10^7 yr for two unbound runaway B stars, consistent with their disk origin where ejection results from a supernova in a binary system or dynamical interactions between massive stars in a dense star cluster. For HVS5, ejection during the first 10^7 yr of its lifetime is ruled out at the 3σ level. Together with the 10^8 yr arrival times inferred for three other well-studied hypervelocity stars (HVSs), these results are consistent with a Galactic center origin for the HVSs. If the HVSs were indeed ejected by the central black hole, then the Galactic center was forming stars ≃200 Myr ago, and the progenitors of the HVSs took ≃100 Myr to enter the black hole's loss cone

Detection of a z=0.0515, 0.0522 absorption system in the QSO S4 0248+430 due to an intervening galaxy

In some of the few cases where the line of sight to a Quasi-Stellar Object (QSO) passes near a galaxy, the galaxy redshift is almost identical to an absorption redshift in the spectrum of the QSO. Although these relatively low redshift QSO-galaxy pairs may not be typical of the majority of the narrow heavy-element QSO absorption systems, they provide a direct measure of column densities in the outer parts of galaxies and some limits on the relative abundances of the gas. Observations are presented here of the QSO S4 0248+430 and a nearby anonymous galaxy (Kuhr 1977). The 14 second separation of the line of sight to the QSO (z sub e = 1.316) and the z=0.052 spiral galaxy, (a projected separation of 20 kpc ((h sub o = 50, q sub o = 0)), makes this a particularly suitable pair for probing the extent and content of gas in the galaxy. Low resolution (6A full width half maximum), long slit charge coupled device (CCD) spectra show strong CA II H and K lines in absorption at the redshift of the galaxy (Junkkarinen 1987). Higher resolution spectra showing both Ca II H and K and Na I D1 and D2 in absorption and direct images are reported here

Role of Physicians in Addressing Food Insecurity in Vermont Seniors

Introduction: This study investigated Vermont physicians’ awareness of - and engagement in – addressing food insecurity experienced by their elderly patients. This information is needed to better understand the role physicians play in solving this problem and to know how education and access to services could ensure that the needs of elders are met in a culturally sensitive manner. Many elders must choose between paying bills, buying medication or buying food. Some elders are unaware that they qualify for food assistance, or would feel stigmatized using it. Nationally, 56% of physicians reported that they were not knowledgeable about food insecurity. Food insecurity can be screened for by using Hunger Free Vermont’s Two Question Screen. Screening, followed by a multidisciplinary team approach with contributions from dietitians, geriatricians, social workers and psychologists may be the most effective way of assessing at-risk patients.https://scholarworks.uvm.edu/comphp_gallery/1214/thumbnail.jp

Genetic susceptibility to Rhodococcus equi

Rhodococcus equi pneumonia is a major cause of morbidity and mortality in neonatal foals. Much effort has been made to identify preventative measures and new treatments for R. equi with limited success. With a growing focus in the medical community on understanding the genetic basis of disease susceptibility, investigators have begun to evaluate the interaction of the genetics of the foal with R. equi. This review describes past efforts to understand the genetic basis underlying R. equi susceptibility and tolerance. It also highlights the genetic technology available to study horses and describes the use of this technology in investigating R. equi. This review provides readers with a foundational understanding of candidate gene approaches, single nucleotide polymorphism-based, and copy number variant-based genome-wide association studies, and next generation sequencing (both DNA and RNA)

Psychometric Properties of the Family Caregiver Delirium Knowledge Questionnaire

A valid, reliable measure of family caregivers’ knowledge about delirium was not located in the literature; such an instrument is essential to assess learning needs and outcomes of education provided. The purpose of the current study was to (a) develop a family Caregiver Delirium Knowledge Questionnaire (CDKQ) based on the Symptom Interpretation Model; and (b) establish validity and reliability of the measure. The 19-item CDKQ was developed and administered to 164 family caregivers for community-dwelling older adults. Descriptive statistics were examined for all variables. Psychometric testing included confirmatory factor analysis, item-to-total correlations, and internal consistency reliability. A three-factor model provided the best fit for the data. The findings support initial validity and reliability of the CDKQ with family caregivers. Although the CDKQ was developed for use with family caregivers, it has potential for use with other caregivers, such as home health aides

Negative-Parity Heavy Pentaquark States in 1/N_c

The 1/N_c expansion for negative-parity heavy pentaquarks is developed using the formalism introduced for excited baryons in large N_c. Relations are found between the mass splittings of these pentaquarks and those of nonexotic baryons.Comment: 14 pages, 3 figures; v2: footnotes and references added, typos corrected; v3: some entries in Table II and equation (12) correcte

Generation of phase-matched circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy

Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, this capability was available only at large-scale X-ray facilities such as synchrotrons. Here we demonstrate the first bright, phase-matched, extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to the linearly polarized high harmonic sources that have been used very successfully for ultrafast element-selective magneto-optic experiments. This work thus represents a critical advance that makes possible element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution, using tabletop-scale setups.Comment: 12 text pages, 4 figures, supplamentary information 6 page

Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution. Circularly-polarized radiation in the extreme ultraviolet (EUV)and soft X-ray spectral regions has proven to be extremelyuseful for investigating chirality-sensitive light–matter inter-actions. It enables studies of chiral molecules using photoelectron circular dichroism1, ultrafast molecular decay dynamics2, the direct measurement of quantum phases (for example, Berry’s phase and pseudo-spin) in graphene and topological insulators3,4 and reconstruction of band structure and modal phases in solids5