National Educators' Workshop. Update 92: Standard Experiments in Engineering Materials Science and Technology

This document contains a collection of experiments presented and demonstrated at the workshop. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

Tin titanate – the hunt for a new ferroelectric perovskite

This work was supported in St Andrews by the Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/P024637/1.We review all the published literature and show that there is no experimental evidence for homogeneous tin titanate SnTiO3 in bulk or thin-film form. Instead a combination of unrelated artefacts are easily misinterpreted. The X-ray Bragg data are contaminated by double scattering from the Si substrate, giving a strong line at the 2-theta angle exactly where perovskite SnTiO3 should appear. The strong dielectric divergence near 560K is irreversible and arises from oxygen site detrapping, accompanied by Warburg/Randles interfacial anomalies. The small (4μC/cm-2) apparent ferroelectric hysteresis remains in samples shown to be pure (Sn,Ti)O2 rutile/cassiterite, in which ferroelectricity is forbidden. Only very recent work reveals real bulk SnTiO3, but it possesses an ilmenite-like structure with an elaborate array of stacking faults, not suitable for ferroelectric devices. Unpublished TEM data reveal an inhomogeneous SnO layered structured thin films, related to shell-core structures. The harsh conclusion is that there is a combination of unrelated artefacts masquerading as ferroelectricity in powders and ALD films; and only a trace of a second phase in PLD film data suggests any perovskite content at all. The fact that X-ray, dielectric, and hysteresis data all lead to the wrong conclusion is instructive and reminds us of earlier work on copper calcium titanate (a well-known boundary-layer capacitor).PostprintPeer reviewe

Scintillation in the Circinus Galaxy water megamasers

We present observations of the 22 GHz water vapor megamasers in the Circinus galaxy made with the Tidbinbilla 70m telescope. These observations confirm the rapid variability seen earlier by Greenhill et al (1997). We show that this rapid variability can be explained by interstellar scintillation, based on what is now known of the interstellar scintillation seen in a significant number of flat spectrum AGN. The observed variability cannot be fully described by a simple model of either weak or diffractive scintillation.Comment: 10 pages, 5 figures. AJ accepte

Gender issues among south African anaesthetists

Objective. To study gender issues among South African anaesthetists.Subjects and design. A postal survey of all registered anaesthetists in South Africa in December 1999.Results. There were 385 respondents out of a potential 960, giving a response rate of 40%; 77 respondents (20%) were female and 308 (80%) were male. The largest group of males was over 50 years old whereas most females were under 50 years. Most respondents chose anaesthesia because of academic appeal or career opportunities. More females reported experiencing sexual harassment and felt discriminated against in terms of job selection during the training period and with regard to referral practices. Most respondents felt that their colleagues did not treat them differently on account of gender but more females felt that both patients and female nurses treated them less favourably than their male colleagues. More males felt supported in their career by their life partners. More females felt that having children adversely affected academic and promotional aspects of their careers. Despite this, females were more likely to have experienced positive benefits from combining parenting with a career and were also more likely to have worked part time, mainly because of domestic commitments. Most respondents were satisfied with their careers, and would choose both medicine and anaesthesia again.Conclusions. Our study suggests that female anaesthetists are generally satisfied with their career choice. However, they are exposed to significant gender-related stresses in the workplace, which are exacerbated by time conflicts for those with children. Allowing part-time employment options and creating a less discriminating environment would enable female doctors to achieve their potential.

Effects of natural light on nitrogen cycling rates in the Mississippi River plume

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110596/1/lno19974220273.pd

Flora of Richmond National Battlefield Park, Virginia

An inventory of the vascular flora of nine of eleven units of Richmond National Battlefield Park was compiled from 1985 to 1987. Each site was visited during the growing season in two to four week intervals; plant species were identified and recorded in the field and/or collected for later study. A total of 761 different species were identified in the surveyed units, and 2487 individual records of species per particular park unit were noted. Twenty-three percent of the flora consists of exotic species, largely from Eurasia. Voucher specimens are housed in the herbaria of the University of Richmond and Virginia Commonwealth University

Logro de resultados personales por personas con discapacidades del desarrollo

En 1993, El Consejo en Calidad y Liderazgo en Apoyos para Personas con Discapacidad (The Council on Quality and Leadership in Supports for People with Disabilities, The Council) desarrolló un instrumento de evaluación de resultados centrado en la persona, Medidas de Resultados Personales (Personal Outcome Measures, 1997). El Council ha conservado en una base de datos (N = 3.630) las entrevistas Medidas de Resultados Personales llevadas a cabo durante sus revisiones de acreditación. El propósito en este artículo es informar de los hallazgos sobre (a) las relaciones entre las Medidas de Resultados Personales (El Council, 1997) y los patrones de logro de resultado individual y (b) examinar el impacto de variables características (discapacidad, tamaño de la organización, tipo de residencia o fuente de financiación del programa) en el logro individual de resultados personales. Se sugieren alternativas para estudiar las dimensiones de la calidad del servicio y la calidad de vida de las personas con discapacidad

New Constraints on the Lyman Continuum Escape Fraction at z~1.3

We examine deep far-ultraviolet (1600 Angstrom) imaging of the Hubble Deep Field-North (HDFN) and the Hubble Ultra Deep Field (HUDF) to search for leaking Lyman continuum radiation from starburst galaxies at z~1.3. There are 21 (primarily sub-L*) galaxies with spectroscopic redshifts between 1.1<z<1.5 and none are detected in the far-UV. We fit stellar population templates to the galaxies' optical/near-infrared SEDs to determine the starburst age and level of dust attenuation, giving an accurate estimate of the intrinsic Lyman continuum ratio, f_1500/f_700, and allowing a conversion from f_700 limits to relative escape fractions. We show that previous high-redshift studies may have underestimated the amplitude of the Lyman Break, and thus the relative escape fraction, by a factor of ~2. Once the starburst age and intergalactic HI absorption are accounted for, 18 galaxies in our sample have limits to the relative escape fraction, f_esc,rel < 1.0 with some limits as low as f_esc,rel < 0.10 and a stacked limit of f_esc,rel < 0.08. This demonstrates, for the first time, that most sub-L* galaxies at high redshift do not have large escape fractions. When combined with a similar study of more luminous galaxies at the same redshift we show that, if all star-forming galaxies at z~1 have similar relative escape fractions, the value must be less than 0.14 (3 sigma). We also show that less than 20% (3 sigma) of star-forming galaxies at z~1 have relative escape fractions near unity. These limits contrast with the large escape fractions found at z~3 and suggest that the average escape fraction has decreased between z~3 and z~1. (Abridged)Comment: Accepted for publication in ApJ. aastex format. 39 pages, 11 figure

Unstable Layers in the Mesopause Region Observed with Na Lidar During the Turbulent Oxygen Mixing Experiment (TOMEX) Campaign

The Na wind/temperature lidar located at Starfire Optical Range near Albuquerque, New Mexico, provided real time measurements of wind, temperature, and Na density in the mesopause region during the TOMEX rocket campaign in October 2000. The state of the atmosphere in which the rocket was launched into was examined using the lidar measurements. Both convectively and dynamically unstable layers were observed at various times and altitudes during the night. The low convective stability region below 90 km was found to be associated with the diurnal tide. The unstable layers are the combined results of wave and tidal perturbations. Comparison with the thermosphere/ionosphere/mesopshere/electrodynamics general circulation model (TIMEGCM) simulation showed that the model can produce the general feature of the observed atmospheric structure (but with a much smaller diurnal amplitude in temperature), which likely leads to underestimate of instability and gravity wave effects