1,670 research outputs found
A Survey of Literature on Genetically Modified Crops: Economics, Ethics and Society
This paper reports on a review of literature in the form of academic papers and published research on ethical and consumer issues for GM crops in North America, with particular emphasis on GM wheat. The issues raised in these papers and the findings and arguments posed by the authors are outlined. A general conclusion that can be drawn from this overview is that public attitudes toward GM foods are diverse and sometimes quite strongly held. The strong negative views of GM food held by some appear to be mainly grounded in individualsâ ethical or moral values. Ethical and risk assessment issues have not been fully explored in the existing literature. There is a general consensus in the applied economics literature that GM crops result in economic benefits, although benefits to individual consumers may not be great enough to overcome perceived risk. Carefully planned provision of credible information informing members of the public of benefits and related issues of concern or costs associated with agricultural biotechnology may have benefits for farm and industry groups, but maintenance of trust in information sources and content is vital to credibility. The discovery and use of genomic techniques that express explicit consumer benefits may lead to more favourable attitudes by many consumers.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies, I00, Q16, Q18,
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On Birthing Dancing Stars: The Need for Bounded Chaos in Information Interaction
While computers causing chaos is acommon social trope, nearly the entirety of the history of computing is dedicated to generating order. Typical interactive information retrieval tasks ask computers to support the traversal and exploration of large, complex information spaces. The implicit assumption is that they are to support users in simplifying the complexity (i.e. in creating order from chaos). But for some types of task, particularly those that involve the creative application or synthesis of knowledge or the creation of new knowledge, this assumption may be incorrect. It is increasingly evident that perfect orderâand the systems we create with itâsupport highly-structured information tasks well, but provide poor support for less-structured tasks.We need digital information environments that help create a little more chaos from order to spark creative thinking and knowledge creation. This paper argues for the need for information systems that offerwhat we term âbounded chaosâ, and offers research directions that may support the creation of such interface
Thermodynamic stability of folded proteins against mutations
By balancing the average energy gap with its typical change due to mutations
for protein-like heteropolymers with M residues, we show that native states are
unstable to mutations on a scale M* ~ (lambda/sigma_mu)^(1/zeta_s), where
lambda is the dispersion in the interaction free energies and sigma_mu their
typical change. Theoretical bounds and numerical estimates (based on complete
enumeration on four lattices) of the instability exponent zeta_s are given. Our
analysis suggests that a limiting size of single-domain proteins should exist,
and leads to the prediction that small proteins are insensitive to random
mutations.Comment: 5 pages, 3 figures, to be published in Physical Review Letter
High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data III: A Color Selected Sample at i^*<20 in the Fall Equatorial Stripe
This is the third paper in a series aimed at finding high-redshift quasars
from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by
the SDSS during its commissioning phase. In this paper, we first present the
observations of 14 bright high-redshift quasars (3.66<z<4.77, i^*<20)
discovered in the SDSS Fall Equatorial Stripe, and the SDSS photometry of two
previously known high-redshift quasars in the same region of the sky. Combined
with the quasars presented in previous papers, we define a color-selected
flux-limited sample of 39 quasars at 3.6 < z < 5.0 and i^*<20, covering a total
effective area of 182 deg^2. From this sample, we estimate the average spectral
power law slope in the rest-frame ultraviolet for quasars at z~4 to be -0.79
with a standard deviation of 0.34, and the average rest-frame equivalent width
of the Ly alpha+N V emission line to be 69 A with a standard deviation of 18 A.
The selection completeness of this multicolor sample is determined from the
model colors of high-redshift quasars, taking into account the distributions of
emission line strengths, intrinsic continuum slope, the line and continuum
absorption from intervening material, and the effects of photometric errors.
The average completeness of this sample is about 75%. The selection function
calculated in this paper will be used to correct the incompleteness of this
color-selected sample and to derive the high-redshift quasar luminosity
function in a subsequent paper. In the Appendix, we present the observations of
an additional 18 faint quasars (3.57<z<4.80, 20.1<i^*<20.8) discovered in the
region on the sky that has been imaged twice. Several quasars presented in this
paper exhibit interesting properties, including a radio-loud quasar at z=4.77,
and a narrow-line quasar (FWHM = 1500 km s^-1) at z=3.57.Comment: AJ accepted (Jan 2001), with minor changes; high-resolution finding
charts available at http://www.sns.ias.edu/~fan/papers/q3.p
A high-throughput analysis of high-resolution X-ray CT images of stems of olive and citrus plants resistant and susceptible to Xylella fastidiosa
The bacterial plant pathogen Xylella fastidiosa causes disease in several globally important crops. However, some cultivars harbour reduced bacterial loads and express few symptoms. Evidence considering plant species in isolation suggests xylem structure influences cultivar susceptibility to X. fastidiosa. We test this theory more broadly by analysing high-resolution synchrotron X-ray computed tomography of healthy and infected plant vasculature from two taxonomic groups containing susceptible and resistant varieties: two citrus cultivars (sweet orange cv. Pera, tangor cv. Murcott) and two olive cultivars (Koroneiki, Leccino). Results found the susceptible plants had more vessels than resistant ones, which could promote within-host pathogen spread. However, features associated with resistance were not shared by citrus and olive. While xylem vessels in resistant citrus stems had comparable diameters to those in susceptible plants, resistant olives had narrower vessels that could limit biofilm spread. And while differences among olive cultivars were not detected, results suggest greater vascular connectivity in resistant compared to susceptible citrus plants. We hypothesize that this provides alternate flow paths for sustaining hydraulic functionality under infection. In summary, this work elucidates different physiological resistance mechanisms between two taxonomic groups, while supporting the existence of an intertaxonomical metric that could speed up the identification of candidate-resistant plants.</p
The Cluster Mass Function from Early SDSS Data: Cosmological Implications
The mass function of clusters of galaxies is determined from 400 deg^2 of
early commissioning imaging data of the Sloan Digital Sky Survey; ~300 clusters
in the redshift range z = 0.1 - 0.2 are used. Clusters are selected using two
independent selection methods: a Matched Filter and a red-sequence color
magnitude technique. The two methods yield consistent results. The cluster mass
function is compared with large-scale cosmological simulations. We find a
best-fit cluster normalization relation of sigma_8*omega_m^0.6 = 0.33 +- 0.03
(for 0.1 ~< omega_m ~< 0.4), or equivalently sigma_8 = (0.16/omega_m)^0.6. The
amplitude of this relation is significantly lower than the previous canonical
value, implying that either omega_m is lower than previously expected (omega_m
= 0.16 if sigma_8 = 1) or sigma_8 is lower than expected (sigma_8 = 0.7 if
omega_m = 0.3). The best-fit mass function parameters are omega_m = 0.19
(+0.08,-0.07) and sigma_8 = 0.9 (+0.3,-0.2). High values of omega_m (>= 0.4)
and low sigma_8 (=~ 2 sigma.Comment: AASTeX, 25 pages, including 7 figures, accepted for publication in
ApJ, vol.585, March 200
The diameter of 88 Thisbe from its occultation of SAO 187124
The 7 October, 1981 occultation of SAO 187124 by 88 Thisbe was observed at twelve sites. The occultation observations, together with information about the asteroid's light curve, gives a mean diameter for Thisbe of 232 + or - 10 km. This value is 10 percent larger than the previously published radiometric diameter of Thisbe
Anderson localization in Bose-Einstein condensates
The understanding of disordered quantum systems is still far from being
complete, despite many decades of research on a variety of physical systems. In
this review we discuss how Bose-Einstein condensates of ultracold atoms in
disordered potentials have opened a new window for studying fundamental
phenomena related to disorder. In particular, we point our attention to recent
experimental studies on Anderson localization and on the interplay of disorder
and weak interactions. These realize a very promising starting point for a
deeper understanding of the complex behaviour of interacting, disordered
systems.Comment: 15 pages review, to appear in Reports on Progress in Physic
Evidence for Reionization at z ~ 6: Detection of a Gunn-Peterson Trough in a z=6.28 Quasar
We present moderate resolution Keck spectroscopy of quasars at z=5.82, 5.99
and 6.28, discovered by the Sloan Digital Sky Survey (SDSS). We find that the
Ly Alpha absorption in the spectra of these quasars evolves strongly with
redshift. To z~5.7, the Ly Alpha absorption evolves as expected from an
extrapolation from lower redshifts. However, in the highest redshift object,
SDSSp J103027.10+052455.0 (z=6.28), the average transmitted flux is
0.0038+-0.0026 times that of the continuum level over 8450 A < lambda < 8710 A
(5.95<z(abs)<6.16), consistent with zero flux. Thus the flux level drops by a
factor of >150, and is consistent with zero flux in the Ly Alpha forest region
immediately blueward of the Ly Alpha emission line, compared with a drop by a
factor of ~10 at z(abs)~5.3. A similar break is seen at Ly Beta; because of the
decreased oscillator strength of this transition, this allows us to put a
considerably stronger limit, tau(eff) > 20, on the optical depth to Ly Alpha
absorption at z=6.
This is a clear detection of a complete Gunn-Peterson trough, caused by
neutral hydrogen in the intergalactic medium. Even a small neutral hydrogen
fraction in the intergalactic medium would result in an undetectable flux in
the Ly Alpha forest region. Therefore, the existence of the Gunn-Peterson
trough by itself does not indicate that the quasar is observed prior to the
reionization epoch. However, the fast evolution of the mean absorption in these
high-redshift quasars suggests that the mean ionizing background along the line
of sight to this quasar has declined significantly from z~5 to 6, and the
universe is approaching the reionization epoch at z~6.Comment: Revised version (2001 Sep 4) accepted by the Astronomical Journal
(minor changes
Early-type galaxies in the SDSS. I. The sample
A sample of nearly 9000 early-type galaxies, in the redshift range 0.01 < z <
0.3, was selected from the Sloan Digital Sky Survey using morphological and
spectral criteria. This paper describes how the sample was selected, presents
examples of images and seeing corrected fits to the observed surface brightness
profiles, describes our method for estimating K-corrections, and shows that the
SDSS spectra are of sufficiently high quality to measure velocity dispersions
accurately. It also provides catalogs of the measured photometric and
spectroscopic parameters. In related papers, these data are used to study how
early-type galaxy observables, including luminosity, effective radius, surface
brightness, color, and velocity dispersion, are correlated with one another.Comment: 63 pages, 21 figures. Accepted by AJ (scheduled for April 2003). This
paper is part I of a revised version of astro-ph/0110344. The full version of
Tables 2 and 3, i.e. the tables listing the photometric and spectroscopic
parameters of ~ 9000 galaxies, are available at
http://astrophysics.phys.cmu.edu/~bernardi/SDSS/Etypes/TABLE
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