144 research outputs found

    Erratum : Levelized cost of CO2 mitigation from hydrogen production routes (Energy Environ. Sci. (2019) 12 (19–40) DOI: 10.1039/C8EE02079E)

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    Some of the references had missing or incorrect details; corrected sections of the affected text are provided below. The reference list has also been corrected and is reproduced in full at the end of this correction. In Section 3.1, ‘‘For literature studies including natural gas supply chain contributions to GHG emissions, the reported total range of LCE values are 10.72–15.86 kg CO2e kg-1 H2 (average of 12.4 of kg CO2e kg-1 H2) 26–34 without CCS and 3.1–5.9 kg CO2e kg-1 H2 (average of 4.3 kg CO2e kg-1 H2) with CCS at 90% capture.27,28,32,33,35’’ should read as ‘‘For literature studies including natural gas supply chain contributions to GHG emissions, the reported total range of LCE values are 10.72–15.86 kg CO2e kg-1 H2 (average of 12.4 of kg CO2e kg-1 H2) 30–38 without CCS and 3.1–5.9 kg CO2e kg-1 H2 (average of 4.3 kg CO2e kg-1 H2) with CCS at 90% capture.31,32,36,37,39’’ ‘‘Direct GHG emissions from the SMR hydrogen production phase are approximately 8–10 t CO2e t-1 H2, 60% of which is generated from the process chemistry, while the remaining 40% arises from heat and power sources required.36’’ should read as ‘‘Direct GHG emissions from the SMR hydrogen production phase are approximately 8–10 t CO2e t-1 H2, 60% of which is generated from the process chemistry, while the remaining 40% arises from heat and power sources required.26’’ ‘‘The majority of CO2 produced exits in two streams, a diluted stream (stack gases with CO2 concentration 5–10 vol%) and a concentrated stream (approximately 50% by vol after pressure swing adsorption).37’’ should read as ‘‘The majority of CO2 produced exits in two streams, a diluted stream (stack gases with CO2 concentration 5–10 vol%) and a concentrated stream (approximately 50% by vol after pressure swing adsorption).27’’ ‘‘If deep decarbonisation is required and emissions must be further reduced from the entire process, then an amine solvent (MEA) based CCS process might be used to capture up to 90% of the CO2 contained in the stack gases,38 although demonstrated removal rates are typically 80%.39’’ should read as ‘‘If deep decarbonisation is required and emissions must be further reduced from the entire process, then an amine solvent (MEA) based CCS process might be used to capture up to 90% of the CO2 contained in the stack gases,28 although demonstrated removal rates are typically 80%.2

    Levelized cost of CO2 mitigation from hydrogen production routes

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    Different technologies produce hydrogen with varying cost and carbon footprints over the entire resource supply chain and manufacturing steps. This paper examines the relative costs of carbon mitigation from a life cycle perspective for 12 different hydrogen production techniques using fossil fuels, nuclear energy and renewable sources by technology substitution. Production costs and life cycle emissions are parameterized and re-estimated from currently available assessments to produce robust ranges to describe uncertainties for each technology. Hydrogen production routes are then compared using a combination of metrics, levelized cost of carbon mitigation and the proportional decarbonization benchmarked against steam methane reforming, to provide a clearer picture of the relative merits of various hydrogen production pathways, the limitations of technologies and the research challenges that need to be addressed for cost-effective decarbonization pathways. The results show that there is a trade-off between the cost of mitigation and the proportion of decarbonization achieved. The most cost-effective methods of decarbonization still utilize fossil feedstocks due to their low cost of extraction and processing, but only offer moderate decarbonisation levels due to previous underestimations of supply chain emissions contributions. Methane pyrolysis may be the most cost-effective short-term abatement solution, but its emissions reduction performance is heavily dependent on managing supply chain emissions whilst cost effectiveness is governed by the price of solid carbon. Renewable electrolytic routes offer significantly higher emissions reductions, but production routes are more complex than those that utilise naturally-occurring energy-dense fuels and hydrogen costs are high at modest renewable energy capacity factors. Nuclear routes are highly cost-effective mitigation options, but could suffer from regionally varied perceptions of safety and concerns regarding proliferation and the available data lacks depth and transparency. Better-performing fossil-based hydrogen production technologies with lower decarbonization fractions will be required to minimise the total cost of decarbonization but may not be commensurate with ambitious climate targets

    Levelized cost of CO2 mitigation from hydrogen production routes

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    Different technologies produce hydrogen with varying cost and carbon footprints over the entire resource supply chain and manufacturing steps. This paper examines the relative costs of carbon mitigation from a life cycle perspective for 12 different hydrogen production techniques using fossil fuels, nuclear energy and renewable sources by technology substitution. Production costs and life cycle emissions are parameterized and re-estimated from currently available assessments to produce robust ranges to describe uncertainties for each technology. Hydrogen production routes are then compared using a combination of metrics, levelized cost of carbon mitigation and the proportional decarbonization benchmarked against steam methane reforming, to provide a clearer picture of the relative merits of various hydrogen production pathways, the limitations of technologies and the research challenges that need to be addressed for cost-effective decarbonization pathways. The results show that there is a trade-off between the cost of mitigation and the proportion of decarbonization achieved. The most cost-effective methods of decarbonization still utilize fossil feedstocks due to their low cost of extraction and processing, but only offer moderate decarbonisation levels due to previous underestimations of supply chain emissions contributions. Methane pyrolysis may be the most cost-effective short-term abatement solution, but its emissions reduction performance is heavily dependent on managing supply chain emissions whilst cost effectiveness is governed by the price of solid carbon. Renewable electrolytic routes offer significantly higher emissions reductions, but production routes are more complex than those that utilise naturally-occurring energy-dense fuels and hydrogen costs are high at modest renewable energy capacity factors. Nuclear routes are highly cost-effective mitigation options, but could suffer from regionally varied perceptions of safety and concerns regarding proliferation and the available data lacks depth and transparency. Better-performing fossil-based hydrogen production technologies with lower decarbonization fractions will be required to minimise the total cost of decarbonization but may not be commensurate with ambitious climate targets

    The University of Michigan cyclotron facility for research in nuclear structure

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    A number of improvements have been made in The University of Michigan 83" sector focused cyclotron since its original construction. The reasons for the changes and the resulting improvement in the production of stable high-quality beams for nuclear research are described. A brief description of the total facility for research in nuclear structure is given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22317/1/0000762.pd

    Impurity Energy Level Within The Haldane Gap

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    An impurity bond JJ{'} in a periodic 1D antiferromagnetic, spin 1 chain with exchange JJ is considered. Using the numerical density matrix renormalization group method, we find an impurity energy level in the Haldane gap, corresponding to a bound state near the impurity bond. When J<JJ{'}<J the level changes gradually from the edge of the Haldane gap to the ground state energy as the deviation dev=(JJ)/Jdev=(J-J{'})/J changes from 0 to 1. It seems that there is no threshold. Yet, there is a threshold when J>JJ{'}>J. The impurity level appears only when the deviation dev=(JJ)/Jdev=(J{'}-J)/J{'} is greater than BcB_{c}, which is near 0.3 in our calculation.Comment: Latex file,9 pages uuencoded compressed postscript including 4 figure

    The absence of ABCA1 decreases soluble ApoE levels but does not diminish amyloid deposition in two murine models of Alzheimer disease.

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    J Biol Chem. 2005 Dec 30;280(52):43243-56. Epub 2005 Oct 5. The absence of ABCA1 decreases soluble ApoE levels but does not diminish amyloid deposition in two murine models of Alzheimer disease. Hirsch-Reinshagen V, Maia LF, Burgess BL, Blain JF, Naus KE, McIsaac SA, Parkinson PF, Chan JY, Tansley GH, Hayden MR, Poirier J, Van Nostrand W, Wellington CL. Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia V4Z 5H5, Canada. Abstract ABCA1, a cholesterol transporter expressed in the brain, has been shown recently to be required to maintain normal apoE levels and lipidation in the central nervous system. In addition, ABCA1 has been reported to modulate beta-amyloid (Abeta) production in vitro. These observations raise the possibility that ABCA1 may play a role in the pathogenesis of Alzheimer disease. Here we report that the deficiency of ABCA1 does not affect soluble or guanidine-extractable Abeta levels in Tg-SwDI/B or amyloid precursor protein/presenilin 1 (APP/PS1) mice, but rather is associated with a dramatic reduction in soluble apoE levels in brain. Although this reduction in apoE was expected to reduce the amyloid burden in vivo, we observed that the parenchymal and vascular amyloid load was increased in Tg-SwDI/B animals and was not diminished in APP/PS1 mice. Furthermore, we observed an increase in the proportion of apoE retained in the insoluble fraction, particularly in the APP/PS1 model. These data suggested that ABCA1-mediated effects on apoE levels and lipidation influenced amyloidogenesis in vivo. PMID: 16207707 [PubMed - indexed for MEDLINE

    Constraints on accelerating universe using ESSENCE and Gold supernovae data combined with other cosmological probes

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    We use recently observed data: the 192 ESSENCE type Ia supernovae (SNe Ia), the 182 Gold SNe Ia, the 3-year WMAP, the SDSS baryon acoustic peak, the X-ray gas mass fraction in clusters and the observational H(z)H(z) data to constrain models of the accelerating universe. Combining the 192 ESSENCE data with the observational H(z)H(z) data to constrain a parameterized deceleration parameter, we obtain the best fit values of transition redshift and current deceleration parameter zT=0.6320.127+0.256z_{T}=0.632^{+0.256}_{-0.127}, q0=0.7880.182+0.182q_{0}=-0.788^{+0.182}_{-0.182}. Furthermore, using Λ\LambdaCDM model and two model-independent equation of state of dark energy, we find that the combined constraint from the 192 ESSENCE data and other four cosmological observations gives smaller values of Ω0m\Omega_{0m} and q0q_{0}, but a larger value of zTz_{T} than the combined constraint from the 182 Gold data with other four observations. Finally, according to the Akaike information criterion it is shown that the recently observed data equally supports three dark energy models: Λ\LambdaCDM, wde(z)=w0w_{de}(z)=w_{0} and wde(z)=w0+w1ln(1+z)w_{de}(z)=w_{0}+w_{1}\ln(1+z).Comment: 18 pages, 8 figure

    Helical distribution of the bacterial chemoreceptor via colocalization with the Sec protein translocation machinery

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    In Escherichia coli, chemoreceptor clustering at a cell pole seems critical for signal amplification and adaptation. However, little is known about the mechanism of localization itself. Here we examined whether the aspartate chemoreceptor (Tar) is inserted directly into the polar membrane by using its fusion to green fluorescent protein (GFP). After induction of Tar–GFP, fluorescent spots first appeared in lateral membrane regions, and later cell poles became predominantly fluorescent. Unexpectedly, Tar–GFP showed a helical arrangement in lateral regions, which was more apparent when a Tar–GFP derivative with two cysteine residues in the periplasmic domain was cross-linked to form higher oligomers. Moreover, similar distribution was observed even when the cytoplasmic domain of the double cysteine Tar–GFP mutant was replaced by that of the kinase EnvZ, which does not localize to a pole. Observation of GFP–SecE and a translocation-defective MalE–GFP mutant, as well as indirect immunofluorescence microscopy on SecG, suggested that the general protein translocation machinery (Sec) itself is arranged into a helical array, with which Tar is transiently associated. The Sec coil appeared distinct from the MreB coil, an actin-like cytoskeleton. These findings will shed new light on the mechanisms underlying spatial organization of membrane proteins in E. coli

    Combined CI+MBPT calculations of energy levels and transition amplitudes in Be, Mg, Ca, and Sr

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    Configuration interaction (CI) calculations in atoms with two valence electrons, carried out in the V(N-2) Hartree-Fock potential of the core, are corrected for core-valence interactions using many-body perturbation theory (MBPT). Two variants of the mixed CI+MBPT theory are described and applied to obtain energy levels and transition amplitudes for Be, Mg, Ca, and Sr

    NRF2 activation reprogrammes defects in oxidative metabolism to restore macrophage function in COPD

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    Rationale: Chronic obstructive pulmonary disease (COPD) is a disease characterized by persistent airway inflammation and disordered macrophage function. The extent to which alterations in macrophage bioenergetics contribute to impaired antioxidant responses and disease pathogenesis has yet to be fully delineated. Objectives: Through the study of COPD alveolar macrophages (AMs) and peripheral monocyte-derived macrophages (MDMs), we sought to establish if intrinsic defects in core metabolic processes drive macrophage dysfunction and redox imbalance. Methods: AMs and MDMs from donors with COPD and healthy donors underwent functional, metabolic, and transcriptional profiling. Measurements and Main Results: We observed that AMs and MDMs from donors with COPD display a critical depletion in glycolytic- and mitochondrial respiration–derived energy reserves and an overreliance on glycolysis as a source for ATP, resulting in reduced energy status. Defects in oxidative metabolism extend to an impaired redox balance associated with defective expression of the NADPH-generating enzyme, ME1 (malic enzyme 1), a known target of the antioxidant transcription factor NRF2 (nuclear factor erythroid 2–related factor 2). Consequently, selective activation of NRF2 resets the COPD transcriptome, resulting in increased generation of TCA cycle intermediaries, improved energetic status, favorable redox balance, and recovery of macrophage function. Conclusions: In COPD, an inherent loss of metabolic plasticity leads to metabolic exhaustion and reduced redox capacity, which can be rescued by activation of the NRF2 pathway. Targeting these defects, via NRF2 augmentation, may therefore present an attractive therapeutic strategy for the treatment of the aberrant airway inflammation described in COPD
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