Infrared observations of periodic comets

Selected comets are observed in the infrared with the NASA Infrared Telescope Facility (IRTF) and other telescopes as appropriate. The scientific objectives are to characterize the thermal emission from the dust coma, derive dust productions rates, detect silicate features near 10 and 20 micrometer, derive average albedo of the grains, and detect changes in grain size or composition with heliocentric distance as well as differences among comets. Knowledge of the dust environment is essential to design and mission planning for NASA's CRAF mission

The nature of cometary grains from remote sensing

Physical property data of cometary grains are derived primarily from thermal emission measurement and optical scattering. Results consistent with the properties of micrometeorites collected in the stratosphere are described

Focus on the future

An assessment is made of what was learned from Halley and recommendations are made for future directions for infrared studies of comets and supporting lab investigations. The following issues are addressed: (1) What steps can be taken to achieve consistent interpretation of Halley infrared data; (2) How successful has the Halley Watch been for infrared studies; (3) What supporting lab research is needed; (4) What are the key infrared observations needed for future comets; and (5) How do current and future NASA programs relate to comet studies

Infrared observations of comets

Selected comets are observed in the near infrared (1 to 2.2 micron) and thermal infrared (3.5 to 20 micron) with the NASA Infrared Telescope Facility (IRTF) and other telescopes as appropriate, in order to characterize the physical properties of the dust grains; their composition, size distribution, emissivity, and albedo. Systematic variations in these properties among comets are looked for, in order to understand the heterogeneity of comet nuclei. Spectrophotometry of the 10 micron silicate emission feature is particularly emphasized. The rate of dust production from the nucleus and its temporal variability are also determined. Knowledge of the dust environment is essential to S/C design and mission planning for NASA's CRAF mission

Quantification of UV stimulated ice chemistry: CO and CO2

Recent laboratory experiments are presented that show that during photolysis of the pure ices there is evidence of the interconversion of CO to CO2 and CO2 to CO using Lyman alpha (1216A) radiation. In addition, there is a substantial amount of another substance being produced. This substance is evident by its infrared absorption peak at 2235 cm(-1). It is believed that this new peak is due to carbon suboxide, C3O2. CO and CO2 have already been detected in comets, and C3O2 has been suggested as a cometary from radiation of CO. Comparisons are made between our results at 1215A and proton radiation experiments and radiation at other wavelengths. The suggestion is that the processing of ices is energy dependent, i.e., dependent on the type of radiation. Several difficult problems have to be solved before these radiation conversions can be quantified. The steps that we are taking to quantify the kinetics are discussed

The Statutory and Constitutional Limits of Using Protected Speech as Evidence of Unlawful Motive Under the National Labor Relations Act

A difficulty inherent in cases under the National Labor Relations Act (NLRA), as in other areas of employment law, is in determining why the employer acted. Perhaps an even harder question, and one too frequently overlooked, is what form of evidence the National Labor Relations Board (NLRB or Board) and any reviewing court properly may consider in determining motive. More specifically, can the Board take into account an employer\u27s vigorous opposition to the union in deciding whether or not a particular action was motivated by antiunion animus? Although common sense suggests yes, several courts of appeals have said no, relying on section 8(c) of the NLRA and on the First Amendment. This Article explores the extent to which protected employer speech under the NLRA may be used to establish unlawful motivation. It does so in the context of a particular category of unfair labor practice cases—those involving the allegedly discriminatory discipline or discharge of union adherents. This category of cases is not only the most common and critical one under the Act, but it also presents questions of employer motive that are not unique to the NLRA

Increasing math talk in adult-child interactions through grocery store signs

There is a persistent gap in math abilities between children from low socioeconomic (SES) families compared to children from high-SES families. Interventions to reduce this gap are often expensive and not easily implemented. This study examined the efficacy of a cost-effective intervention in grocery stores in order to try and increase the number of math-related adult-child conversations to increase children’s school readiness. We created and placed signs about general language and math in grocery stores in a low-SES neighborhood and a high-SES neighborhood that encouraged conversations between adults and children while shopping. Researchers used observational coding methods to see how these signs naturally influenced conversations. When signs that contained prompts to engage in math conversations were present there was an overall increase in conversations about math compared to the general language signs or when no signs were posted. When signs were present in the low-SES location, there was an increase in conversations about math between adults and children, whereas the signs did not have this effect in the high-SES location. This study demonstrates the benefits of implementing a cost-effective intervention in a natural environment that could increase math conversations and school readiness in children, especially from low-SES families

Cometary dust composition

The earth based measurements and in situ sampling of Comet Halley have provided new data about the chemical composition of cometary grains. Recent progress in laboratory studies of interplanetary dust particles (IDPs) complement the comet data, allowing inferences about the mineralogy and physical structure of the comet dust to be drawn from the observed elemental composition and infrared spectra. The in situ dust composition measurements at Halley, the composition of IDPs and their relation to comet dust, and the origin of the 3.4 micron hydrocarbon feature is discussed. Related discussion is also presented on aromatic components in comets and the 3.4 micron feature. These topics are briefly summarized

The Proper Role of After-Aquired Evidence in Employment Discrimination Litigation

A new defense to employment discrimination claims has gained acceptance in the lower courts. Employers who allegedly have discriminated against their employees because of race, sex or age are winning judgments on the basis of after-acquired evidence of employee misconduct. The evidence is “after-acquired” in the sense that the misconduct was unknown to the employer at the time the alleged discrimination occurred but was acquired later, often through the use of discovery devices in the employee\u27s discrimination action. Lower courts have accepted the proposition that if the employer would have discharged the plaintiff on the basis of the after-acquired evidence, then the defendant is not liable for employment discrimination, and the plaintiff, accordingly, is entitled to no relief. This Article criticizes the approach to the after-acquired evidence defense that is emerging in the lower courts. The Article rejects the premise that a plaintiff must be “fire proof” in order to prevail in an employment discrimination action. It argues that after-acquired evidence of a plaintiff\u27s misconduct should have no impact on an employer\u27s liability for discrimination. In liability determinations, the focus should be on what the employer actually did and not on what the employer might have done had it not discriminated. Discriminatory conduct causes harm and deserves legal condemnation even when the conduct would have been justifiable on other grounds

A Survey of 10-Micron Silicate Emission from Dust around Young Sun-Like Stars

We obtained low resolution (R = 100) mid-infrared (8-13 micron wavelengths) spectra of 8 nearby young main sequence stars with the Keck 1 telescope and Long-Wavelength Spectrometer (LWS) to search for 10 micron silicate (Si-O stretch) emission from circumstellar dust. No stars exhibited readily apparent emission: Spectra were then analyzed by least-squares fitting of a template based on a spectrum of Comet Hale-Bopp. Using this technique, we were able to constrain the level of silicate emission to a threshold ten times below what was previously possible from space. We found one star, HD 17925, with a spectrum statistically different from its calibrator and consistent with a silicate emission peak of 7% of the photosphere at a wavelength of 10 microns. Excess emission at 60 microns from this star has already been reported.Comment: 19 total pages, 5 Postscript figures, 2 tables, Late