Coherent Raman spectroscopies for measuring molecular flow velocity

Various types of coherent Raman spectroscopy are characterized and their application to molecular flow velocity and direction measurement and species concentration and temperature determination is discussed

Coherent Raman spectroscopy for supersonic flow measurments

In collaboration with NASA/Langley Research Center, a truly nonintrusive and nonseeding method for measuring supersonic molecular flow parameters was proposed and developed at Colorado State University. The feasibility of this Raman Doppler Velocimetry (RDV), currently operated in a scanning mode, was demonstrated not only in a laboratory environment at Colorado State University, but also in a major wind tunnel at NASA/Langley Research Center. The research progress of the RDV development is summarized. In addition, methods of coherent Rayleigh-Brillouin spectroscopy and single-pulse coherent Raman spectroscopy are investigated, respectively, for measurements of high-pressure and turbulent flows

An Inventory of Disability Information for the Population Living in Institutions

The population living in institutions is excluded from most major national surveys. We evaluate the implications of this exclusion for disability statistics and research by compiling and examining existing disability information for the population living in institutions, with an emphasis on working-age people. The population living in institutions is a very small share of the entire population, but increased considerably from 1990 to 2000, especially for those ages 18-64. Working-age people accounted for a much larger proportion of the population living in institutions in 2000 (56 percent) than in 1990 (45 percent). As of 2000, 86 percent of the institutionalized working-age population resided in correctional institutions, and the remaining 14 percent were approximately evenly split between nursing homes and other institutions, many of which specialize in care for people with disabilities. When disability is defined as having at least one of the four disabilities in the 2000 Census—self-care, mental, physical, or sensory disabilities—the vast majority of the population with disabilities lives in household units; 8.7 percent live in group quarters (GQs), 6.4 percent live in institutional GQs, and 2.3 percent in non-institutional GQs. For working-age people with disabilities, the share of males living in institutional GQs is much larger than the share of females (7.7 percent versus 1.7 percent), in part reflecting the fact that more than nine out of ten inmates in correctional institutions are male. Working-age people with disabilities residing in institutional GQs are also disproportionately African American (38.6 percent of those ages 18-49 and 22.4 percent of those ages 50-64). Increased incarceration rates and the relatively high prevalence of disability in the incarcerated population suggest that growth in incarceration could have a substantial impact on disability prevalence in the household population, and on the characteristics of the household population with disabilities, most notably for young male African Americans. The nursing home residence rate declined for all age groups, but for those under 65 the decline is very small relative to the size of all persons in that age group, and thus seems unlikely to have much impact on disability statistics for the household population. We found no surveys covering the population living in institutions other than correctional institutions and nursing homes. The lack of information on this population may present a substantial problem for disability statistics and research

Clumpy and fractal shocks, and the generation of a velocity dispersion in molecular clouds

We present an alternative explanation for the nature of turbulence in molecular clouds. Often associated with classical models of turbulence, we instead interpret the observed gas dynamics as random motions, induced when clumpy gas is subject to a shock. From simulations of shocks, we show that a supersonic velocity dispersion occurs in the shocked gas provided the initial distribution of gas is sufficiently non-uniform. We investigate the velocity size-scale relation $\sigma \propto r^{\alpha}$ for simulations of clumpy and fractal gas, and show that clumpy shocks can produce realistic velocity size-scale relations with mean $\alpha \thicksim 0.5$. For a fractal distribution, with a fractal dimension of 2.2 similar to what is observed in the ISM, we find $\sigma \propto r^{0.4}$. The form of the velocity size-scale relation can be understood as due to mass loading, i.e. the post-shock velocity of the gas is determined by the amount of mass encountered as the gas enters the shock. We support this hypothesis with analytical calculations of the velocity dispersion relation for different initial distributions. A prediction of this model is that the line-of sight velocity dispersion should depend on the angle at which the shocked gas is viewed.Comment: 11 pages, 17 figures, accepted for publication in MNRA

Chandra Survey of Nearby Galaxies: A Significant Population of Candidate Central Black Holes in Late-type Galaxies

Based on the Chandra data archive as of March 2016, we have identified 314 candidate active galactic nuclei in 719 galaxies located closer than 50 Mpc, among them late-type (Hubble types Sc and later) galaxies that previously had been classified from optical observations as containing star-forming (H II) nuclei. These late-type galaxies comprise a valuable subsample to search for low-mass (<~ 10^6 solar masses) central black holes. For the sample as a whole, the overall dependence of the fraction of active nuclei on galaxy type and nuclear spectral classification is consistent with previous results based on optical surveys. We detect 51 X-ray cores among the 163 H II nuclei and estimate that, very conservatively, ~74% of them with luminosities above 10^38 erg/s are not contaminated by X-ray binaries; the fraction increases to ~92% for X-ray cores with a luminosity of 10^39 erg/s or higher. This allows us to estimate a black hole occupation fraction of >~ 21% in these late-type, many bulgeless, galaxies.Comment: ApJ to appea

Chandra Survey of Nearby Galaxies: The Catalog

We searched in the public archive of the Chandra X-ray Observatory as of March 2016 and assembled a sample of 719 galaxies within 50 Mpc with ACIS observations available. By cross-correlation with the optical or near-infrared nuclei of these galaxies, 314 of them are identified to have an X-ray active galactic nucleus (AGN). The majority of them are low-luminosity AGNs and are unlikely X-ray binaries based upon their spatial distribution and luminosity functions. The AGN fraction is around 60% for elliptical galaxies and early-type spirals, but drops to roughly 20% for Sc and later types, consistent with previous findings in the optical. However, the X-ray survey is more powerful in finding weak AGNs, especially from regions with active star formation that may mask the optical AGN signature. For example, 31% of the H II nuclei are found to harbor an X-ray AGN. For most objects, a single power-law model subject to interstellar absorption is adequate to fit the spectrum, and the typical photon index is found to be around 1.8. For galaxies with a non-detection, their stacked Chandra image shows an X-ray excess with a luminosity of a few times 10^37 erg/s on average around the nuclear region, possibly composed of faint X-ray binaries. This paper reports on the technique and results of the survey; in-depth analysis and discussion of the results will be reported in forthcoming papers.Comment: Accepted for publication in the Astrophysical Journa

IR pumped third-harmonic generation and sum-frequency generation in diatomic molecules

The potential efficiency of using nonlinear up-conversion techniques for the high efficiency type lasers (CO,CO2, and chemical) is assessed. Results indicate that: the small pump photon energy necessitates the use of molecular media for conversion if resonance enhancement is to be used and that molecular systems present several problems. These difficulties include: their levels are complex; their transition probabilities are often unknown; and the oscillator strengths among vibrational levels in the ground electronic state of a molecule are much smaller than those among electronic states of an atom, thus limiting the magnitude of nonlinear interactions. It is shown that this problem can be eliminated by making use of vibronic transitions which, being primarily electronic transitions have much larger matrix elements and efficient conversion can be achieved with molecular systems

Organisational Use of Social Media and Stakeholder Engagement

This thesis consists of three empirical studies examining how social media are used by corporations, advocacy non-governmental organisations (A-NGOs) and hybrid organisations to engage with stakeholders and enhance stakeholder accountability. The first study examines the use of social media by corporations to disclose CSR information and manage stakeholder perceptions. Drawing on organised hypocrisy and organisational theory and through the analysis of Facebook posts from S&P100 companies, this study finds that CSR actions disclosures attract both positive and negative stakeholder reactions. CSR talk and decisions disclosures generate positive reactions and reduce negative perceptions. It is also evident that the reputational façade in CSR disclosures is more likely to attract positive reactions and less likely to attract negative reactions than the rational façade. The progressive façade is more likely to attract positive reactions than the rational façade, and it is more likely to attract negative reactions than the reputational façade. Overall, the findings suggest that corporations employ various strategies in social media CSR disclosures to manage stakeholder perceptions and maintain legitimacy. The second study examines the use of social media by A-NGOs to attract stakeholder engagement, and whether such engagement leads to large-scale stakeholder support outside social media platforms. This study draws on Castells’ (2013) network-making power perspective and employs a unique dataset of Greenpeace signups (i.e. the proxy for stakeholder support) to the “Save the Arctic” (STA) petition from over 236 countries and a sample of 8,336 Greenpeace Facebook messages related to the STA campaigns in 29 languages. The findings suggest that Greenpeace communicates advocacy information that appeals to logic and emotions to attract stakeholder engagement. In examining the social impacts of A-NGO social media engagement, the level of national stakeholder support is positively associated with the effectiveness of advocacy information in attracting stakeholder engagement at the Facebook account level. The level of global stakeholder support is positively associated with both the effectiveness and global dissemination of advocacy information at the Facebook network level. Overall, this study affirms that social media can assist A-NGOs in engaging with stakeholders and obtaining their support on advocated issues on a large scale, thereby enhancing downward accountability. The last study focuses on the use of social media by a type of hybrid organisation - B Corp - and examines the effect of its governance mechanisms on social media engagement activities. B Corp firms face a mission drift risk in which financial objectives may overshadow CSR considerations. This study posits that B Corp’s legal responsibility, ethical standards and mission-alignment policies positively influence the extent and quality of its social media engagement. After analysing CSR-related tweets posted by 1,074 U.S. B Corp firms certified between 2014 and 2018 and those posted by stakeholders towards the firm, it is found that the quality of social media engagement is positively associated with B Corp’s legal responsibility, ethical standards and mission-alignment policies. In addition, this study finds that the extent of social media engagement is positively associated with mission-alignment policies. Overall, the findings highlight the importance of B Corp’s governance mechanisms in improving stakeholder accountability

Velocity measurements by laser resonance fluorescence

The photonburst correlation method was used to detect single atoms in a buffer gas. Real time flow velocity measurements with laser induced resonance fluorescence from single or multiple atoms was demonstrated and this method was investigated as a tool for wind tunnel flow measurement. Investigations show that single atoms and their real time diffusional motion on a buffer gas can be measured by resonance fluorescence. By averaging over many atoms, flow velocities up to 88 m/s were measured in a time of 0.5 sec. It is expected that higher flow speeds can be measured and that the measurement time can be reduced by a factor of 10 or more by careful experimental design. The method is clearly not ready for incorporation in high speed wind tunnels because it is not yet known whether the stray light level will be higher or lower, and it is not known what detection efficiency can be obtained in a wind tunnel situation