13,494 research outputs found
Strengthening impact assessment: a call for integration and focus
We suggest that the impact assessment community has lost its way based on our observation that impact assessment is under attack because of a perceived lack of efficiency. Specifically, we contend that the proliferation of different impact assessment types creates separate silos of expertise and feeds arguments for not only a lack of efficiency but also a lack of effectiveness of the process through excessive specialisation and a lack of interdisciplinary practice. We propose that the solution is a return to the basics of impact assessment with a call for increased integration around the goal of sustainable development and focus through better scoping. We rehearse and rebut counter arguments covering silo-based expertise, advocacy, democracy, sustainability understanding and communication. We call on the impact assessment community to rise to the challenge of increasing integration and focus, and to engage in the debate about the means of strengthening impact assessment
Identification of key molecular properties of reactive NDMA precursors using computational chemistry
Spin Hall Conductance of the Two Dimensional Hole Gas in a Perpendicular Magnetic Field
The charge and spin Hall conductance of the two-dimensional hole gas within
the Luttinger model with and without inversion symmetry breaking terms in a
perpendicular magnetic field are studied, and two key phenomena are predicted.
The sign of the spin Hall conductance is modulated periodically by the external
magnetic field, which means a possible application in the future. Furthermore,
a resonant spin Hall conductance in the two-dimensional hole gas with a certain
hole density at a typical magnetic field is indicated, which implies a likely
way to firmly establish the intrinsic spin Hall effect. The charge Hall
conductance is unaffected by the spin-orbit coupling.Comment: accepted for publication in Phys. Rev. B; 6 pages, 4 figure
The Imprint of Gravitational Waves on the Cosmic Microwave Background
Long-wavelength gravitational waves can induce significant temperature
anisotropy in the cosmic microwave background. Distinguishing this from
anisotropy induced by energy density fluctuations is critical for testing
inflationary cosmology and theories of large-scale structure formation. We
describe full radiative transport calculations of the two contributions and
show that they differ dramatically at angular scales below a few degrees. We
show how anisotropy experiments probing large- and small-angular scales can
combine to distinguish the imprint due to gravitational waves.Comment: 11 pages, Penn Preprint-UPR-
Lipid droplet detection by the cavity perturbation method
There are currently no point-of-care diagnosis strategies available to indicate the presence of neoplasmic growth. This research aims to develop a novel diagnostic strategy based on detecting TAG accumulation in cells. This element of the research is a preliminary experiment to prove the concept of detecting TAG lipid droplets in YEPD media. It was found that a change in mono-unsaturated concentration can be detected by the frequency shift in a resonant cavity. The dielectric constant of TAG vegetable oils was calculated at 2.34-2.39. It was also found that concentrations of lipid droplet can be differentiated up to 5% (v/v)
Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host Star
We present the results of HST observations of the host star for the first
definitive extrasolar planet detected by microlensing. The light curve model
for this event predicts that the lens star should be separated from the source
star by ~6mas at the time of the HST images. If the lens star is a late G, K or
early M dwarf, then it will be visible in the HST images as an additional
source of light that is blended with the source image. Unless the lens and
source have exactly the same colors, its presence will also be revealed by a
systematic shift between centroids of the source plus lens in different filter
bands. The HST data indicates both of these effects: the HST source that
matches the position of the source star is 0.21 magnitudes brighter in the
ACS/HRC-F814W filter than the microlensing model predicts, and there is an
offset of ~0.7mas between the centroid of this source in the F814W and F435W
filter bands. We conclude the planetary host star has been detected in these
HST images, and this identification of the lens star enables a complete
solution of the lens system. The lens parameters are determined with a Bayesian
analysis, averaging over uncertainties in the measured parameters, interstellar
extinction, and allowing for the possibility of a binary companion to the
source star. This yields a stellar mass of M_* = 0.63(+0.07/-0.09) M_solar and
a planet mass of M_p = 2.6 (+0.8/-0.6) M_Jup at an orbital separation of 4.3
(+2.5/-0.8) AU. Thus, the lens system resembles our own Solar System, with a
planet of ~3 Jupiter-masses in a Jupiter-like orbit around a star of two-thirds
of a Solar mass. These conclusions can be tested with future HST images, which
should reveal a broadening of the blended source-plus-lens point spread
function due to the relative lens-source proper motion.Comment: 11 pages, with 3 figures. to appear in ApJ Lett (Aug 20 issue
Post-AGB Stars in Globular Clusters and Galactic Halos
We discuss three aspects of post-AGB (PAGB) stars in old populations. (1) HST
photometry of the nucleus of the planetary nebula (PN) K 648 in the globular
cluster (GC) M15 implies a mass of 0.60 Msun, in contrast to the mean masses of
white dwarfs in GCs of ~0.5 Msun. This suggests that K 648 is descended from a
merged binary, and we infer that single Pop II stars do not produce visible
PNe. (2) Yellow PAGB stars are the visually brightest stars in old populations
(Mv ~ -3.3) and are easily recognizable because of their large Balmer jumps;
thus they show great promise as a Pop II standard candle. Two yellow PAGB stars
in the GC NGC 5986 have the same V magnitudes to within +/-0.05 mag, supporting
an expected narrow luminosity function. (3) Using CCD photometry and a u filter
lying below the Balmer jump, we have detected yellow PAGB stars in the halo of
M31 and in its dwarf elliptical companion NGC 205. With the Milky Way zero
point, we reproduce the Cepheid distance to M31, and find that NGC 205 is ~100
kpc further away than M31. The star counts imply a yellow PAGB lifetime of
about 25,000 yr, and their luminosities imply masses near 0.53 Msun.Comment: 6 pages, 2 figures. To appear in proceedings of Torun, Poland,
workshop on "Post-AGB Objects (Proto-Planetary Nebulae) as a Phase of Stellar
Evolution," ed. S.K. Gorn
Fast, exact CMB power spectrum estimation for a certain class of observational strategies
We describe a class of observational strategies for probing the anisotropies
in the cosmic microwave background (CMB) where the instrument scans on rings
which can be combined into an n-torus, the {\em ring torus}. This class has the
remarkable property that it allows exact maximum likelihood power spectrum
estimation in of order operations (if the size of the data set is )
under circumstances which would previously have made this analysis intractable:
correlated receiver noise, arbitrary asymmetric beam shapes and far side lobes,
non-uniform distribution of integration time on the sky and partial sky
coverage. This ease of computation gives us an important theoretical tool for
understanding the impact of instrumental effects on CMB observables and hence
for the design and analysis of the CMB observations of the future. There are
members of this class which closely approximate the MAP and Planck satellite
missions. We present a numerical example where we apply our ring torus methods
to a simulated data set from a CMB mission covering a 20 degree patch on the
sky to compute the maximum likelihood estimate of the power spectrum
with unprecedented efficiency.Comment: RevTeX, 14 pages, 5 figures. A full resolution version of Figure 1
and additional materials are at http://feynman.princeton.edu/~bwandelt/RT
Biodesalination: an emerging technology for targeted removal of Na+and Clâfrom seawater by cyanobacteria
Although desalination by membrane processes is a possible solution to the problem of freshwater supply, related cost and energy demands prohibit its use on a global scale. Hence, there is an emerging necessity for alternative, energy and cost-efficient methods for water desalination. Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies. Moreover, cyanobacteria can grow with minimal nutrient requirements and under natural sunlight. Taking these observations together, a consortium of five British Universities was formed to test the principle of using cyanobacteria as ion exchangers, for the specific removal of Na+ and Clâ from seawater. This project consisted of the isolation and characterisation of candidate strains, with central focus on their potential to be osmotically and ionically adaptable. The selection panel resulted in the identification of two Euryhaline strains, one of freshwater (Synechocystis sp. Strain PCC 6803) and one of marine origin (Synechococcus sp. Strain PCC 7002) (Robert Gordon University, Aberdeen). Other work packages were as follows. Genetic manipulations potentially allowed for the expression of a light-driven, Clâ-selective pump in both strains, therefore, enhancing the bioaccumulation of specific ions within the cell (University of Glasgow). Characterisation of surface properties under different salinities (University of Sheffield), ensured that cellâliquid separation efficiency would be maximised post-treatment, as well as monitoring the secretion of mucopolysaccharides in the medium during cell growth. Work at Newcastle University is focused on the social acceptance of this scenario, together with an assessment of the potential risks through the generation and application of a Hazard Analysis and Critical Control Points plan. Finally, researchers in Imperial College (London) designed the process, from biomass production to water treatment and generation of a model photobioreactor. This multimodal approach has produced promising first results, and further optimisation is expected to result in mass scaling of this process
Aquadi-u-chloro-bis(diethylenetriamine)dicopper(11) dichloride: A redetermination at 180 K
The structure of the title compound, [Cu2Cl2(C4H13N3)2(H2O)]Cl2, at 180 K is described in space group P21/n with a unit-cell volume twice that reported previously for the structure at 293 K [Willett (2001[Willett, R. D. (2001). Acta Cryst. E57, m605-m606.]). Acta Cryst. E57, m605-m606]. In the smaller unit cell, in space group P21/m, the complex has imposed mirror symmetry and unusually elongated displacement ellipsoids. At 180 K, refinement in the larger unit cell with no imposed symmetry resolves this issue. With room-temperature data collected from the same crystal, however, refinement using the larger unit cell gives no significant improvement, and the previously reported structure is considered to be most appropriate
- âŠ