1,247 research outputs found
Bars in Disk-Dominated and Bulge-Dominated Galaxies at z~0: New Insights from ~3600 SDSS Galaxies
We present a study of large-scale bars in the local Universe, based on a
large sample of ~3692 galaxies, with -18.5 <= M_g < -22.0 mag and redshift 0.01
<= z < 0.03, drawn from the Sloan Digitized Sky Survey. Our sample includes
many galaxies that are disk-dominated and of late Hubble types. Both color cuts
and S\'ersic cuts yield a similar sample of ~2000 disk galaxies. We
characterize bars and disks by ellipse-fitting r-band images and applying
quantitative criteria. After excluding highly inclined () systems,
we find the following results. (1) The optical r-band fraction (f_opt-r) of
barred galaxies, when averaged over the whole sample, is ~48%-52%. (2) When
galaxies are separated according to half light radius (r_e), or normalized
r_e/R_24, which is a measure of the bulge-to-disk (B/D) ratio, a remarkable
result is seen: f_opt-r rises sharply, from ~40% in galaxies that have small
r_e/R_24 and visually appear to host prominent bulges, to ~70% for galaxies
that have large r_e/R_24 and appear disk-dominated. (3) rises
for galaxies with bluer colors (by ~30%) and lower masses (by ~15%-20%). (4)
While hierarchical CDM models of galaxy evolution models fail to
produce galaxies without classical bulges, our study finds that ~20% of disk
galaxies appear to be ``quasi-bulgeless''. (5) After applying the same cutoffs
in magnitude (M_V= 1.5 kpc), and bar ellipticity
(e_bar >=~0.4) that studies out to z~1 apply to ensure a complete sample,
adequate spatial resolution, and reliable bar identification, we obtain an
optical r-band bar fraction of 34%. This is comparable to the value reported at
z~0.2-1.0, implying that the optical bar fraction does not decline dramatically
by an order of magnitude in bright galaxies out to z~1. (abridged)Comment: accepted for publication in ApJ, 50 pages, 20 figure
Constraints on Bars in the Local Universe from 5000 SDSS Galaxies
We present the first study of bars in the local Universe, based on the Sloan
Digitized Sky Survey (SDSS). The large sample of ~5000 local galaxies provides
the largest study to date of local bars and minimizes the effect of cosmic
variance. The sample galaxies have M_g<=-18.5 mag and cover the redshift range
0.01<=z<0.04. We use a color cut in the color-magnitude diagram and the Sersic
index n to identify disk galaxies. We characterize bars and disks using r-band
images and the method of iterative ellipse fits and quantitative criteria
developed in Jogee at al. (2004, ApJL, 615, L105). After excluding highly
inclined (i>60 degrees) systems our results are: (1) the optical (r-band)
fraction of barred galaxies among local disk galaxies is 43%, which confirms
the ubiquity of local bars, in agreement with other optical studies based on
smaller samples (e.g.Eskridge et al. 2000, AJ, 119, 536, Marinova & Jogee 2006,
astro-ph/0608039); (2) the optical bar fraction rises for bluer galaxies,
suggesting a relation between bars and star formation; (3) preliminary analyzes
suggest that the optical bar fraction increases steeply with the galaxy
effective radius; (4) the optical bar fraction at z~0 is ~35% for bright disks
(M_g0.4), large-scale (bar semi-major
axis >1.5 kpc) bars, which is comparable to the value of 30+/-6% reported
earlier (Jogee et al. 2004) for similar disks and bars at z~0.2-1.0.Comment: 1 page, Proceedings of the IAU Symposium No. 235, 2006, "Galaxy
Evolution across the Hubble Time", F. Combes & J. Palous, ed
Analysis on the evolution and governance of the biotechnology industry of China
The past twenty years have witnessed the high-speed growth of China’s biotechnology industry, and this presents an excellent opportunity to examine the changes that have taken place, especially, to carry out overall evaluation and governance analysis from the perspective of technology policies. Although China’s biotechnology industry has achieved tremendous extension both in scale and structure, the strengths it gained from basic research have been significantly weakened by commercialization. This has resulted in the comparatively limited scale of the whole industry, innovation-lacking products, poor output from research and development and scarcity of industrial resources. A large range of literature regarding China’s biotechnology industry attributes these outcomes to vague and even inappropriate governance, findings supported mainly by analyses based on the linear model of impact of government policies on industrial development. In these analyses, government, enterprises and companies as well as R&D organizations are either put on the opposite poles or in a straight line.
After examining the nature of China’s biotechnology industry, and in particular the dynamic procedures in research and development, the authors of this paper argue that besides government, enterprises and R&D organizations, a diverse array of factors should be taken into account as we tackle issues emerging in understanding the development of China’s biotechnology industry. Furthermore, these factors, human or nonhuman, should not be arranged as opposing poles or linearly connected points on a straight line. They are in fact all knitted in networks and act as both knitters and knots.
China’s biotechnology industry gains its strength to develop and evolve from these networks, thus its governance must be aimed at improving their stability and quality.
Although the main disciplinary perspectives of this research are historical and sociological (including identification of the three development stages of biotechnology in China since 1978 to present days), a large number of concepts and ideas from management studies as well as an interdisciplinary approach are also incorporated into the analysis.
The main model used in this research is Actor Network Theory, which is employed as a basic theoretical frame. From this starting point the authors attempt to make a closer examination of China’s biotechnology industry both at the level of technology research and development and at the level of commercialization. The modeling process in this research can be regarded as an attempt to explore the social construction of China’s biotechnology industry. The paper reveals how China’s biotechnology industry develops in the form of networks within the country’s social context and what kinds of relationships exist among the relevant factors; therefore, providing guiding insights for improving the governance of China’s biotechnology industry both in policy and management
A Look at Women and Abortion in the United States
The issue of abortion is defined by ethical questions and, often, controversial views. This paper argues the importance of a coherent and enhanced effort to study the quantitative relationship between women’s characteristics and the average number of abortions in the United States. It specifically looks at the average number of previous abortions and socioeconomic and demographic characteristics, as this relationship has not been explored before in the existing literature. We expect to establish a correlation between the average number of previous abortions and characteristics such as age, marital status, income and highest degree of education completed. An empirical model is developed, and then studied using regression analysis. Even though this study has limitations stemming from the nature of the data and the methodology employed, it illustrates that variables such as age, marital status, religion and education, employment status, income, and metropolitan status do influence the number of previous abortions a woman has had. The broader implications of this study suggest that the issue of abortion should be addressed with a clear focus on the most interested party, namely, women
Renewable energy power system at Swan Valley Nyungah Community: Industry or community innovation?
The paper presents a case study in renewable energy application, namely the renewable energy power system installed in the Swan Valley Nyungah Community (SVNC) in Perth, Western Australia. The objectives of the 1998 project, which involved the Perth based International Centre for Application of Solar Energy (CASE), were to provide electricity in a culturally acceptable form, reduce power costs and demonstrate the viability of the renewable energy technology used. The outcomes, however, did not match the expectations of the Aboriginal community or the Alternative Energy Development Board. The industry representatives did not have site specific knowledge for the implementation of their technology. The local end-users were not involved in the project itself. For projects like this to work, high professional responsibility, transparent accountability and community participation and acceptance of the technology should accompany good intentions
Bibliometric modelling and policy making
Bibliometric methods for analysing and describing research output have been in existence and usage for over half a century. This has been supported internationally by the establishment and operations of organisations such as the Institute for Scientific Information (ISI) and the continual release and calculations of journal lists, bibliometric indicators and rankings. More recently bibliometric analyses have responded to the changes posed by the growing field of Internet publishing by incorporating some electronic versions of journals. Policy makers in Australia have been relying on such bibliometric information and analyses in making funding decisions and encouraging the development of research potential and strengths. This raises a number of concerns. Does bibliometric modelling of research productivity reflect the real impact research has for Australia's future? Is the electronic word in all its varieties overpowering the printed word? Is the grey literature as important as the officially recognised prestigious publications? Are the expectations policy makers, policy executives and managers draw from bibliometric modelling justified? The paper attempts to provide some answers to these questions based on a study of three Australian research centres in the field of the geosciences. The analysis reveals a number of anomalies in the generalisations made when ISI models are used for policy decisions
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