Laser frequency combs for astronomical observations

A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at about 1.5 micrometers - beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.Comment: Science, 5th September 2008. 18 pages, 7 figures (7 JPG files), including Supporting Online Material. Version with higher resolution figures available at http://astronomy.swin.edu.au/~mmurphy/pub.htm

Women's Perceptions of Contributory Factors for Not Achieving a Vaginal Birth After Cesarean (VBAC)

BACKGROUND: With cesarean rates around the world escalating, concern is growing around why women wanting a vaginal birth after cesarean (VBAC) are not achieving their goal. AIM: To gain an understanding of women’s perceptions of factors they felt contributed to not achieving a VBAC. SETTING AND PARTICIPANTS: Fifteen women were interviewed following a nonelective repeat cesarean section (NERCS). They had attended a Western Australian midwifery-led service, next birth after cesarean (NBAC), and labored but were not successful in achieving a VBAC because of reasons around delayed progress. Interview transcripts were analyzed using Colaizzi’s method of thematic analysis. FINDINGS: Five themes emerged: “Tentative commitment with lingering doubts,” “My body failed me,” “Compromised by a longer than tolerable labor,” “Unable to effectively self-advocate in a climate of power struggling and poor support,” and “The inflexibility of hospital processes.” The final theme included two subthemes: “Restrictive policies” on labor and use of the cardiotocography, “The CTG.” CONCLUSIONS: When labor did not progress as envisaged and hospital processes adversely affected how women were supported, women’s doubts around being able to achieve a VBAC were reinforced with a NERCS. Maternity services need to ensure clinical practice reflects best evidence while assuring staff are supportive of women’s choice

A convolution of observational and model data to estimate age of air spectra in the northern hemispheric lower stratosphere

Derivation of mean age of air (AoA) and age spectra from atmospheric measurements remains a challenge and often requires output from atmospheric models. This study tries to minimize the direct influence of model output and presents an extension and application of a previously established inversion method to derive age spectra from mixing ratios of long- and short-lived trace gases. For a precise description of cross-tropopause transport processes, the inverse method is extended to incorporate air entrainment into the stratosphere across the tropical and extratropical tropopause. We first use simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) to provide a general proof of concept of the extended principle in a controllable and consistent environment, where the method is applied to an idealized set of 10 trace gases with predefined constant lifetimes and compared to reference model age spectra. In the second part of the study we apply the extended inverse method to atmospheric measurements of multiple long- and short-lived trace gases measured aboard the High Altitude and Long Range (HALO) research aircraft during the two research campaigns POLSTRACC–GW-LCYCLE–SALSA (PGS) and Wave-driven Isentropic Exchange (WISE). As some of the observed species undergo significant loss processes in the stratosphere, a Monte Carlo simulation is introduced to retrieve age spectra and chemical lifetimes in stepwise fashion and to account for the large uncertainties. Results show that in the idealized model scenario the inverse method retrieves age spectra robustly on annual and seasonal scales. The extension to multiple entry regions proves reasonable as our CLaMS simulations reveal that in the model between 50 % and 70 % of air in the lowermost stratosphere has entered through the extratropical tropopause (30–90∘ N and S) on annual average. When applied to observational data of PGS and WISE, the method derives age spectra and mean AoA with meaningful spatial distributions and quantitative range, yet large uncertainties. Results indicate that entrainment of fresh tropospheric air across both the extratropical and tropical tropopause peaked prior to both campaigns, but with lower mean AoA for WISE than PGS data. The ratio of moments for all retrieved age spectra for PGS and WISE is found to range between 0.52 and 2.81 years. We conclude that the method derives reasonable and consistent age spectra using observations of chemically active trace gases. Our findings might contribute to an improved assessment of transport with age spectra in future studies

Pregnancy experiences of Western Australian women attending a specialist childbirth and mental illness antenatal clinic

Our purpose was to explore the pregnancy experiences of Australian women attending a specialized Childbirth and Mental Illness (CAMI) antenatal clinic. A qualitative exploratory design was selected to give voice to women with a severe mental illness receiving antenatal care. Telephone interviews with 41 women, 24 primiparous and 17 multiparous, were analysed using thematic analysis. Three themes emerged: ‘Building relationships’, ‘Acknowledged me as a person with special needs’ and ‘Respect and understanding without stigma’. Findings offer insight into care experiences possible within a multidisciplinary model developed to addresses psychiatric and obstetric needs of pregnant women with severe mental illness

Evaluating GAIA performances on eclipsing binaries. I. Orbits and stellar parameters for V505 Per, V570 Per and OO Peg

The orbits and physical parameters of three detached, double-lined A-F eclipsing binaries have been derived combining H_P, V_T, B_T photometry from the Hipparcos/Tycho mission with 8500-8750 Ang ground-based spectroscopy, mimicking the photometric+spectroscopic observations that should be obtained by GAIA, the approved Cornerstone 6 mission by ESA. This study has two main objectives, namely (a) to derive reasonable orbits for a number of new eclipsing binaries and (b) to evaluate the expected performances by GAIA on eclipsing binaries and the accuracy achievable on the determination of fundamental stellar parameters like masses and radii. It is shown that a 1% precision in the basic stellar parameters can be achieved by GAIA on well observed detached eclipsing binaries provided that the spectroscopic observations are performed at high enough resolution. Other types of eclipsing binaries (including semi-detached and contact types) and different spectral types will be investigated in following papers along this series.Comment: A&A, 11 pages, 5 figures, 5 table

Peer Mentoring: Benefits to First-Time College Students and Their Peer Mentors

The experiences of first-year, first-time college students are impacted by a variety of challenges that pose a threat to student success and retention. One intervention universities are implementing to address these challenges are peer mentorship programs. While the benefits to first-time students of peer mentorship programs are well-researched, there is a lack of research on the benefits for mentors themselves. The purpose of this study was to examine the perceived and demonstrable benefits for peer mentors working within a first-year seminar. This mixed-methods study assessed both first-time student achievement outcomes (i.e., first-term GPA and one-year persistence; N = 7,154) as well as the professional and personal development benefits of peer mentors (n = 52). Results showed first-time students who participated in the peer mentor program had significantly higher student achievement and peer mentors themselves had increased academic self-efficacy, improved communication, leadership, and interpersonal presence, and strengthened social and professional networks