903 research outputs found
Sorption Properties of Greenwaste Biochar for Two Triazine Pesticides
This work by ISTC’s Wei Zheng and Kishore Rajagopalan and collaborators from Delaware State University provides innovative solutions for producing energy and food in a sustainable environment. Renewable energy can be produced by converting greenwaste such as using highway grass clippings for gasoline or biodiesel through a process called pyrolysis (heating to 450°C with limited oxygen) and then implementing some refining techniques. However, the pyrolysis process produces a byproduct called biochar, which is a carbon-rich substance similar to activated carbon. The biochar byproduct could be landfilled, but the researchers have a better idea.The other aspect of this research is determining how to produce food without contaminating the environment. The researchers considered two common pesticides. Atrazine and simazine are used as broad-spectrum pesticides/herbicides for agricultural, recreational, and residential uses, but the most common use is for field crop applications. These pesticides can inadvertently contaminate water ways and water bodies from rain events and soil erosion. To prevent this contamination, the researchers proposed mixing biochar into the soil to prevent pesticide/herbicide loss from the field. Full results published in Zheng, Wei, et al (2010). "Sorption properties of greenwaste biochar for two triazine pesticides." Journal of Hazardous Materials 181(1-3), 121-126. https://doi.org/10.1016/j.jhazmat.2010.04.103Ope
Induced CMB quadrupole from pointing offsets
Recent claims in the literature have suggested that the {\it WMAP} quadrupole
is not primordial in origin, and arises from an aliasing of the much larger
dipole field because of incorrect satellite pointing. We attempt to reproduce
this result and delineate the key physics leading to the effect. We find that,
even if real, the induced quadrupole would be smaller than claimed. We discuss
reasons why the {\it WMAP} data are unlikely to suffer from this particular
systematic effect, including the implications for observations of point
sources. Given this evidence against the reality of the effect, the similarity
between the pointing-offset-induced signal and the actual quadrupole then
appears to be quite puzzling. However, we find that the effect arises from a
convolution between the gradient of the dipole field and anisotropic coverage
of the scan direction at each pixel. There is something of a directional
conspiracy here -- the dipole signal lies close to the Ecliptic Plane, and its
direction, together with the {\it WMAP} scan strategy, results in a strong
coupling to the component in Ecliptic co-ordinates. The dominant
strength of this component in the measured quadrupole suggests that one should
exercise increased caution in interpreting its estimated amplitude. The {\it
Planck} satellite has a different scan strategy which does not so directly
couple the dipole and quadrupole in this way and will soon provide an
independent measurement.Comment: 8 pages, 4 figure
Expanding Insight into Asymmetric Palladium-Catalyzed Allylic Alkylation of N-Heterocyclic Molecules and Cyclic Ketones
Eeny, meeny, miny … enaminones! Lactams and imides have been shown to consistently provide enantioselectivities substantially higher than other substrate classes previously investigated in the palladium-catalyzed asymmetric decarboxylative allylic alkylation. Several new substrates have been designed to probe the contributions of electronic, steric, and stereoelectronic factors that distinguish the lactam/imide series as superior alkylation substrates (see scheme). These studies culminated in marked improvements on carbocyclic allylic alkylation substrates
Microlensing Results Challenge the Core Accretion Runaway Growth Scenario for Gas Giants
We compare the planet-to-star mass-ratio distribution measured by
gravitational microlensing to core accretion theory predictions from population
synthesis models. The core accretion theory's runaway gas accretion process
predicts a dearth of intermediate-mass giant planets that is not seen in the
microlensing results. In particular, the models predict fewer
planets at mass ratios of than inferred
from microlensing observations. This tension implies that gas giant formation
may involve processes that have hitherto been overlooked by existing core
accretion models or that the planet-forming environment varies considerably as
a function of host-star mass. Variation from the usual assumptions for the
protoplanetary disk viscosity and thickness could reduce this discrepancy, but
such changes might conflict with microlensing results at larger or smaller mass
ratios, or with other observations. The resolution of this discrepancy may have
important implications for planetary habitability because it has been suggested
that the runaway gas accretion process may have triggered the delivery of water
to our inner solar system. So, an understanding of giant planet formation may
help us to determine the occurrence rate of habitable planets.Comment: 12 pages, 2 figures, 1 table, accepted for publication in ApJ
Observational Consequences of a Landscape
In this paper we consider the implications of the "landscape" paradigm for
the large scale properties of the universe. The most direct implication of a
rich landscape is that our local universe was born in a tunnelling event from a
neighboring vacuum. This would imply that we live in an open FRW universe with
negative spatial curvature. We argue that the "overshoot" problem, which in
other settings would make it difficult to achieve slow roll inflation, actually
favors such a cosmology.
We consider anthropic bounds on the value of the curvature and on the
parameters of inflation. When supplemented by statistical arguments these
bounds suggest that the number of inflationary efolds is not very much larger
than the observed lower bound. Although not statistically favored, the
likelihood that the number of efolds is close to the bound set by observations
is not negligible. The possible signatures of such a low number of efolds are
briefly described.Comment: 21 pages, 4 figures v2: references adde
Grouping practices in the primary school: what influences change?
During the 1990s, there was considerable emphasis on promoting particular kinds of pupil grouping as a means of raising educational standards. This survey of 2000 primary schools explored the extent to which schools had changed their grouping practices in responses to this, the nature of the changes made and the reasons for those changes. Forty eight percent of responding schools reported that they had made no change. Twenty two percent reported changes because of the literacy hour, 2% because of the numeracy hour, 7% because of a combination of these and 21% for other reasons. Important influences on decisions about the types of grouping adopted were related to pupil learning and differentiation, teaching, the implementation of the national literacy strategy, practical issues and school self-evaluation
Constraining noncommutative field theories with holography
An important window to quantum gravity phenomena in low energy noncommutative
(NC) quantum field theories (QFTs) gets represented by a specific form of UV/IR
mixing. Yet another important window to quantum gravity, a holography,
manifests itself in effective QFTs as a distinct UV/IR connection. In matching
these two principles, a useful relationship connecting the UV cutoff
, the IR cutoff and the scale of
noncommutativity , can be obtained. We show that an effective
QFT endowed with both principles may not be capable to fit disparate
experimental bounds simultaneously, like the muon and the masslessness of
the photon. Also, the constraints from the muon preclude any possibility
to observe the birefringence of the vacuum coming from objects at cosmological
distances. On the other hand, in NC theories without the UV completion, where
the perturbative aspect of the theory (obtained by truncating a power series in
) becomes important, a heuristic estimate of the region
where the perturbative expansion is well-defined , gets affected when holography is applied by providing the energy of the
system a -dependent lower limit. This may affect models
which try to infer the scale by using data from low-energy
experiments.Comment: 4 pages, version to be published in JHE
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