25,489 research outputs found
Pyrolysis-catalytic reforming/gasification of waste tires for production of carbon nanotubes and hydrogen
The production of high-value carbon nanotubes and hydrogen from the two-stage pyrolysis catalytic-steam reforming/gasification of waste tires have been investigated. The catalysts used were Co/Alâ Oâ , Cu/Alâ Oâ , Fe/Alâ Oâ and Ni/Alâ Oâ . The pyrolysis temperature and catalyst temperature were 600 °C and 800 °C, respectively. The fresh catalysts were analysed by temperature programmed reduction and X-ray diffraction. The product gases, including hydrogen were analysed by gas chromatography and the carbon nanotubes characterized by scanning and transmission electron microscopy and Raman spectrometry. The results showed that the Ni/Alâ Oâ catalyst produced high quality multiwalled carbon nanotubes along with the highest Hâ yield of 18.14 mmol gâ»Âč tire, compared with the other catalysts, while the Co/Alâ Oâ and Cu/Alâ Oâ catalysts produced lower hydrogen yield, which is suggested to be associated with the formation of amorphous type carbons on the surface of the Co/Alâ Oâ and Cu/Alâ Oâ catalyst
ASTROD and ASTROD I -- Overview and Progress
In this paper, we present an overview of ASTROD (Astrodynamical Space Test of
Relativity using Optical Devices) and ASTROD I mission concepts and studies.
The missions employ deep-space laser ranging using drag-free spacecraft to map
the gravitational field in the solar-system. The solar-system gravitational
field is determined by three factors: the dynamic distribution of matter in the
solar system; the dynamic distribution of matter outside the solar system
(galactic, cosmological, etc.) and gravitational waves propagating through the
solar system. Different relativistic theories of gravity make different
predictions of the solar-system gravitational field. Hence, precise
measurements of the solar-system gravitational field test all these. The tests
and observations include: (i) a precise determination of the relativistic
parameters beta and gamma with 3-5 orders of magnitude improvement over
previous measurements; (ii) a 1-2 order of magnitude improvement in the
measurement of G-dot; (iii) a precise determination of any anomalous, constant
acceleration Aa directed towards the Sun; (iv) a measurement of solar angular
momentum via the Lense-Thirring effect; (v) the detection of solar g-mode
oscillations via their changing gravity field, thus, providing a new eye to see
inside the Sun; (vi) precise determination of the planetary orbit elements and
masses; (viii) better determination of the orbits and masses of major
asteroids; (ix) detection and observation of gravitational waves from massive
black holes and galactic binary stars in the frequency range 0.05 mHz to 5 mHz;
and (x) exploring background gravitational-waves.Comment: 17 pages, 6 figures, presented to The Third International ASTROD
Symposium on Laser Astrodynamics, Space Test of Relativity and
Gravitational-Wave Astronomy, Beijing, July 14-16, 2006; International
Journal of Modern Physics D, in press (2008
Modelling trade offs between public and private conservation policies
To reduce global biodiversity loss, there is an urgent need to determine the
most efficient allocation of conservation resources. Recently, there has been a
growing trend for many governments to supplement public ownership and
management of reserves with incentive programs for conservation on private
land. At the same time, policies to promote conservation on private land are
rarely evaluated in terms of their ecological consequences. This raises
important questions, such as the extent to which private land conservation can
improve conservation outcomes, and how it should be mixed with more traditional
public land conservation. We address these questions, using a general framework
for modelling environmental policies and a case study examining the
conservation of endangered native grasslands to the west of Melbourne,
Australia. Specifically, we examine three policies that involve: i) spending
all resources on creating public conservation areas; ii) spending all resources
on an ongoing incentive program where private landholders are paid to manage
vegetation on their property with 5-year contracts; and iii) splitting
resources between these two approaches. The performance of each strategy is
quantified with a vegetation condition change model that predicts future
changes in grassland quality. Of the policies tested, no one policy was always
best and policy performance depended on the objectives of those enacting the
policy. This work demonstrates a general method for evaluating environmental
policies and highlights the utility of a model which combines ecological and
socioeconomic processes.Comment: 20 pages, 5 figure
The Circumstellar Environment of High Mass Protostellar Objects. III Evidence of Infall?
The results are presented of a molecular line survey to search for the
spectral signature of infall towards 77 850 micron continuum sources believed
to be candidate high mass protostellar objects. Up to six different
transitions, HCO+ 1-0, 3-2 and 4-3, H2CO 2_12-1_11, N2H+ and H13CO+ 3-2, were
observed towards each source. Towards the peak of the 850 micron emission, N2H+
was typically strong, with a peak antenna temperature of ~1.5K, with a typical
linewidth of ~2km/s. The good agreement between the velocity and velocity width
of the N2H+ and H13CO+ emission suggests that both species are tracing similar
material in the sources. With respect to the velocity of the N2H+, there is a
statistically significant excess of blue asymmetric line profiles in both the
HCO+ 1-0 and H2CO transitions. This excess reaches levels similar to that seen
towards samples of low mass protostars, and suggests that the material around
these high mass sources is infalling. We identify 22 promising candidate infall
sources which show at least one blue asymmetric line profile and no red
asymmetric profiles. The infall velocity is estimated to be in the range of 0.1
km/s to 1 km/s with an implied mass accretion rate of between 2x10^{-4} Msol/yr
and 10^{-3}Msol/yr.Comment: Accepted for publication in Astronomy and Astrophysics. Higher
resolution versions of Figures 1 and 2 are available from
http://www.jb.man.ac.uk/~gaf/Papers.htm
Extreme Food-Plant Specialisation in Megabombus Bumblebees as a Product of Long Tongues Combined with Short Nesting Seasons
© 2015 Huang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. http://creativecommons.org/licenses/by/4.0/ The attached file is the published version of the article
Broadband dielectric spectroscopy on benzophenone: alpha relaxation, beta relaxation, and mode coupling theory
We have performed a detailed dielectric investigation of the relaxational
dynamics of glass-forming benzophenone. Our measurements cover a broad
frequency range of 0.1 Hz to 120 GHz and temperatures from far below the glass
temperature well up into the region of the small-viscosity liquid. With respect
to the alpha relaxation this material can be characterized as a typical
molecular glass former with rather high fragility. A good agreement of the
alpha relaxation behavior with the predictions of the mode coupling theory of
the glass transition is stated. In addition, at temperatures below and in the
vicinity of Tg we detect a well-pronounced beta relaxation of Johari-Goldstein
type, which with increasing temperature develops into an excess wing. We
compare our results to literature data from optical Kerr effect and depolarized
light scattering experiments, where an excess-wing like feature was observed in
the 1 - 100 GHz region. We address the question if the Cole-Cole peak, which
was invoked to describe the optical Kerr effect data within the framework of
the mode coupling theory, has any relation to the canonical beta relaxation
detected by dielectric spectroscopy.Comment: 11 pages, 7 figures; revised version with new Fig. 5 and some smaller
changes according to referees' demand
Intracranial EEG fluctuates over months after implanting electrodes in human brain.
OBJECTIVE: Implanting subdural and penetrating electrodes in the brain causes acute trauma and inflammation that affect intracranial electroencephalographic (iEEG) recordings. This behavior and its potential impact on clinical decision-making and algorithms for implanted devices have not been assessed in detail. In this study we aim to characterize the temporal and spatial variability of continuous, prolonged human iEEG recordings.
APPROACH: Intracranial electroencephalography from 15 patients with drug-refractory epilepsy, each implanted with 16 subdural electrodes and continuously monitored for an average of 18 months, was included in this study. Time and spectral domain features were computed each day for each channel for the duration of each patient\u27s recording. Metrics to capture post-implantation feature changes and inflexion points were computed on group and individual levels. A linear mixed model was used to characterize transient group-level changes in feature values post-implantation and independent linear models were used to describe individual variability.
MAIN RESULTS: A significant decline in features important to seizure detection and prediction algorithms (mean line length, energy, and half-wave), as well as mean power in the Berger and high gamma bands, was observed in many patients over 100 d following implantation. In addition, spatial variability across electrodes declines post-implantation following a similar timeframe. All selected features decreased by 14-50% in the initial 75 d of recording on the group level, and at least one feature demonstrated this pattern in 13 of the 15 patients. Our findings indicate that iEEG signal features demonstrate increased variability following implantation, most notably in the weeks immediately post-implant.
SIGNIFICANCE: These findings suggest that conclusions drawn from iEEG, both clinically and for research, should account for spatiotemporal signal variability and that properly assessing the iEEG in patients, depending upon the application, may require extended monitoring
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