217 research outputs found
Implications of Emerging Vehicle Technologies on Rare Earth Supply and Demand in the United States
We explore the long-term demand and supply potentials of rare earth elements in alternative energy vehicles (AEVs) in the United States until 2050. Using a stock-flow model, we compare a baseline scenario with scenarios that incorporate an exemplary technological innovation: a novel aluminumâceriumâmagnesium alloy. We find that the introduction of the novel alloy demonstrates that even low penetration rates can exceed domestic cerium production capacity, illustrating possible consequences of technological innovations to material supply and demand. End-of-life vehicles can, however, overtake domestic mining as a source of materials, calling for proper technologies and policies to utilize this emerging source. The long-term importing of critical materials in manufactured and semi-manufactured products shifts the location of material stocks and hence future secondary supply of high-value materials, culminating in a double benefit to the importing country. This modeling approach is adaptable to the study of varied scenarios and materials, linking technologies with supply and demand dynamics in order to understand their potential economic and environmental consequence
Nanostructural characterization of geopolymers by advanced beamline techniques
This paper presents the outcomes of a series of beamline-based studies, the results of which are combined to provide a more detailed multiscale understanding of the structure and chemistry of geopolymer binders.
The range of beamline-based characterization techniques which have been applied to the study of geopolymer binders is increasing rapidly; although no single technique can provide a holistic view of binder structure across all the length scales which are of importance in determining strength development and durability, the synergy achievable through the combination of multiple beamline techniques is leading to rapid advances in knowledge in this area. Studies based around beamline infrared and X-ray fluorescence microscopy, in situ and ex situ neutron pair distribution function analysis, and nano- and micro-tomography, are combined to provide an understanding of geopolymer gel chemistry, nano- and microstructure in two and three dimensions, and the influences of seeded nucleation and precursor chemistry in these key areas.
The application of advanced characterization methods in recent years has brought the understanding of geopolymer chemistry from a point, not more than a decade ago, when the analysis of the detailed chemistry of the aluminosilicate binder gel was considered intractable due to its disordered (âX-ray amorphousâ) nature, to the present day where the influence of key compositional parameters on nanostructure is well understood, and both gel structure and reaction kinetics can be manipulated through methods including seeding, temperature variation, and careful mix design.
This paper therefore provides a review outlining the value of nanotechnology â and particularly nanostructural characterization â in the development and optimization of a new class of environmentally beneficial cements and concretes. Key engineering parameters, in particularly strength development and permeability, are determined at a nanostructural level, and so it is essential that gel structures can be analyzed and manipulated at this level; beamline-based characterization techniques are critical in providing the ability to achieve this goal
Neural correlates of probabilistic category learning in patients with schizophrenia
Functional neuroimaging studies of probabilistic category learning in healthy adults report activation of cortical-striatal circuitry. Based on previous findings of normal learning rate concurrent with an overall performance deficit in patients with schizophrenia, we hypothesized that relative to healthy adults, patients with schizophrenia would display preserved caudate nucleus and abnormal prefrontal cortex activation during probabilistic category learning. Forty patients with schizophrenia receiving antipsychotic medication and 25 healthy participants were assessed on interleaved blocks of probabilistic category learning and control tasks while undergoing blood oxygenation level-dependent functional magnetic resonance imaging. In addition to the whole sample of patients with schizophrenia and healthy adults, a subset of patients and healthy adults matched for good learning was also compared. In the whole sample analysis, patients with schizophrenia displayed impaired performance in conjunction with normal learning rate relative to healthy adults. The matched comparison of patients and healthy adults classified as good learners revealed greater caudate and dorsolateral prefrontal cortex activity in the healthy adults and greater activation in a more rostral region of the dorsolateral prefrontal, cingulate, parahippocampal and parietal cortex in patients. These results demonstrate that successful probabilistic category learning can occur in the absence of normal frontal-striatal function. Based on analyses of the patients and healthy adults matched on learning and performance, a minority of patients with schizophrenia achieve successful probabilistic category learning and performance levels through differential activation of a circumscribed neural network which suggests a compensatory mechanism in patients showing successful learning. Copyright © 2009 Society for Neuroscience
Magnetic fields and Sunyaev-Zel'dovich effect in galaxy clusters
In this work we study the contribution of magnetic fields to the Sunyaev
Zeldovich (SZ) effect in the intracluster medium. In particular we calculate
the SZ angular power spectrum and the central temperature decrement. The effect
of magnetic fields is included in the hydrostatic equilibrium equation by
splitting the Lorentz force into two terms one being the force due to magnetic
pressure which acts outwards and the other being magnetic tension which acts
inwards. A perturbative approach is adopted to solve for the gas density
profile for weak magnetic fields (< 4 micro G}). This leads to an enhancement
of the gas density in the central regions for nearly radial magnetic field
configurations. Previous works had considered the force due to magnetic
pressure alone which is the case only for a special set of field
configurations. However, we see that there exists possible sets of
configurations of ICM magnetic fields where the force due to magnetic tension
will dominate. Subsequently, this effect is extrapolated for typical field
strengths (~ 10 micro G) and scaling arguments are used to estimate the angular
power due to secondary anisotropies at cluster scales. In particular we find
that it is possible to explain the excess power reported by CMB experiments
like CBI, BIMA, ACBAR at l > 2000 with sigma_8 ~ 0.8 (WMAP 5 year data) for
typical cluster magnetic fields. In addition we also see that the magnetic
field effect on the SZ temperature decrement is more pronounced for low mass
clusters ( ~ 2 keV). Future SZ detections of low mass clusters at few arc
second resolution will be able to probe this effect more precisely. Thus, it
will be instructive to explore the implications of this model in greater detail
in future works.Comment: 20 pages, 8 figure
Corrections to flat-space particle dynamics arising from space granularity
The construction of effective Hamiltonians describing corrections to flat
space particle dynamics arising from the granularity of space at very short
distances is discussed in the framework of an heuristic approach to the
semiclassical limit of loop quantum gravity. After some general motivation of
the subject, a brief non-specialist introduction to the basic tools employed in
the loop approach is presented. The heuristical semiclassical limit is
subsequently defined and the application to the case of photons and spin 1/2
fermions is described. The resulting modified Maxwell and Dirac Hamiltonians,
leading in particular to Planck scale corrections in the energy-momentum
relations, are presented. Alternative interpretations of the results and their
limitations, together with other approaches are briefly discussed along the
text. Three topics related to the above methods are reviewed: (1) The
determination of bounds to the Lorentz violating parameters in the fermionic
sector, obtained from clock comparison experiments.(2) The calculation of
radiative corrections in preferred frames associated to space granularity in
the framework of a Yukawa model for the interactions and (3) The calculation of
synchrotron radiation in the framework of the Myers-Pospelov effective theories
describing Lorentz invariance violations, as well as a generalized approach to
radiation in Planck scale modified electrodynamics. The above exploratory
results show that quantum gravity phenomenology provides observational guidance
in the construction of quantum gravity theories and opens up the possibility of
probing Planck scale physics.Comment: 49 pages, 6 figures and 4 tables. Extended version of the talk given
at the 339-th WE-Heraeus-Seminar: Special Relativity, will it survive the
next 100 years?, Potsdam, february 200
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Morphology and foliar chemistry of containerized Abies fraseri (Pursh) Poir. seedlings as affected by water availability and nutrition
âą We present the results of a two-year (2007â2008) greenhouse study investigating the
effect of water availability and nitrogen fertilization on the growth, biomass
partitioning, and foliar nutrient content of Abies fraseri (Pursh)
Poir.
âą Fertilizer and moisture content (irrigation) were varied in a factorial experiment
combining four levels of irrigation and three levels of fertilization to evaluate growth
and foliar nutrient content. In addition, a numerical optimization was used to estimate
appropriate levels of each factor necessary to achieve simulated goals for response
variables.
âą Irrigation increased the height growth by 12 to 35% depending on the fertilization
treatment (p = 0.0001). Fertilization increased height growth by 10 to
26% (p = 0.02). A similar response was observed for stem diameter growth
(SDG). Total biomass accumulation increased as result of positive response of stem and
root biomass development, and foliar nitrogen content was positively affected by nitrogen
fertilization and negatively affected by irrigation. The numerical optimization for
simulated target growth and nitrogen content responses produced levels of input
combinations with high desirability factors to achieve the target responses.
âą These results suggest that nutrient addition is a strong determining factor for early
development of this species. The improved growth efficiency in this study is likely
attributed to a combination of factors including, improved photosynthetic capacity,
decreased stomatal limitations, or increased resource allocation to stems
Morphology and foliar chemistry of containerized Abies fraseri (Pursh) Poir. seedlings as affected by water availability and nutrition
Non-thermal processes in cosmological simulations
Non-thermal components are key ingredients for understanding clusters of
galaxies. In the hierarchical model of structure formation, shocks and
large-scale turbulence are unavoidable in the cluster formation processes.
Understanding the amplification and evolution of the magnetic field in galaxy
clusters is necessary for modelling both the heat transport and the dissipative
processes in the hot intra-cluster plasma. The acceleration, transport and
interactions of non-thermal energetic particles are essential for modelling the
observed emissions. Therefore, the inclusion of the non-thermal components will
be mandatory for simulating accurately the global dynamical processes in
clusters. In this review, we summarise the results obtained with the
simulations of the formation of galaxy clusters which address the issues of
shocks, magnetic field, cosmic ray particles and turbulence.Comment: 27 pages, 16 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 15; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Genome-wide association study identifies 30 Loci Associated with Bipolar Disorder
This paper is dedicated to the memory of Psychiatric Genomics Consortium (PGC) founding member and Bipolar disorder working group co-chair Pamela Sklar. We thank the participants who donated their time, experiences and DNA to this research, and to the clinical and scientific teams that worked with them. We are deeply indebted to the investigators who comprise the PGC. The views expressed are those of the authors and not necessarily those of any funding or regulatory body. Analyses were carried out on the NL Genetic Cluster Computer (http://www.geneticcluster.org ) hosted by SURFsara, and the Mount Sinai high performance computing cluster (http://hpc.mssm.edu).Bipolar disorder is a highly heritable psychiatric disorder. We performed a genome-wide association study including 20,352 cases and 31,358 controls of European descent, with follow-up analysis of 822 variants with P<1x10-4 in an additional 9,412 cases and 137,760 controls. Eight of the 19 variants that were genome-wide significant (GWS, p < 5x10-8) in the discovery GWAS were not GWS in the combined analysis, consistent with small effect sizes and limited power but also with genetic heterogeneity. In the combined analysis 30 loci were GWS including 20 novel loci. The significant loci contain genes encoding ion channels, neurotransmitter transporters and synaptic components. Pathway analysis revealed nine significantly enriched gene-sets including regulation of insulin secretion and endocannabinoid signaling. BDI is strongly genetically correlated with schizophrenia, driven by psychosis, whereas BDII is more strongly correlated with major depressive disorder. These findings address key clinical questions and provide potential new biological mechanisms for BD.This work was funded in part by the Brain and Behavior Research Foundation, Stanley Medical Research Institute, University of Michigan, Pritzker Neuropsychiatric Disorders Research Fund L.L.C., Marriot Foundation and the Mayo Clinic Center for Individualized Medicine, the NIMH Intramural Research Program; Canadian Institutes of Health Research; the UK Maudsley NHS Foundation Trust, NIHR, NRS, MRC, Wellcome Trust; European Research Council; German Ministry for Education and Research, German Research Foundation IZKF of MĂŒnster, Deutsche Forschungsgemeinschaft, ImmunoSensation, the Dr. Lisa-Oehler Foundation, University of Bonn; the Swiss National Science Foundation; French Foundation FondaMental and ANR; Spanish Ministerio de EconomĂa, CIBERSAM, Industria y Competitividad, European Regional Development Fund (ERDF), Generalitat de Catalunya, EU Horizon 2020 Research and Innovation Programme; BBMRI-NL; South-East Norway Regional Health Authority and Mrs. Throne-Holst; Swedish Research Council, Stockholm County Council, Söderström Foundation; Lundbeck Foundation, Aarhus University; Australia NHMRC, NSW Ministry of Health, Janette M O'Neil and Betty C Lynch
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