Search

Your search keyword '"Mitchell, John F."' showing total 264 results
Start Over Author "Mitchell, John F."
264 results on '"Mitchell, John F."'

51. Thermal Conductivity: Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5 Sr0.5 CoO3−δ(Adv. Funct. Mater. 47/2017)

Author

Wu, Xuewang, primary, Walter, Jeff, additional, Feng, Tianli, additional, Zhu, Jie, additional, Zheng, Hong, additional, Mitchell, John F., additional, Biškup, Neven, additional, Varela, Maria, additional, Ruan, Xiulin, additional, Leighton, Chris, additional, and Wang, Xiaojia, additional

Published
2017
Full Text
View/download PDF

54. Pen portraits of Presidents – Sir Basil John Mason, CB, DSc, FRS.

Author

Folland, Chris K. and Mitchell, John F. B.

Subjects
*CLOUD physics, *PORTRAITS, *BASIL, *PENS, *CLIMATE change
Abstract

We present a short biography of Sir John Mason, part of Weather's series of pen portraits of Past Presidents of the Royal Meteorological Society. This biography is longer than a normal pen portrait to reflect Sir John Mason's exceptional and wide‐ranging achievements and to show how he contributed to the debate about climate change. We include a discussion of his early years, particularly his pioneering work in cloud physics. We particularly review the key activities of the Met Office with which he was closely involved in his years as Director General, followed by his activities after retirement and his main awards. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

55. Approaches to the electronic structure of incommensurately modulated insulating crystals.

Author

Mitchell, John F. and Burdett, Jeremy K.

Subjects
*CRYSTALS, *ELECTRONIC structure, *CRYSTALLOGRAPHY, *PERTURBATION theory
Abstract

A one-dimensional model of an incommensurately modulated insulator is investigated in perturbation theory using tight-binding theory with overlap. Results applicable in the sinusoidal regime are discussed in terms of the ‘‘structural resonance’’ of McConnell and Heine (Ref. ). The method of moments is used to explore ordering in one-dimensional chains, suggesting a novel electronic explanation of the driving force for the transition from disorder to order as a function of electron count (band filling). © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
1995
Full Text
View/download PDF

56. Order–disorder transitions and the method of moments.

Author

Burdett, Jeremy K. and Mitchell, John F.

Subjects
*MOMENTS method (Statistics), *CRYSTALS, *ELECTRON distribution
Abstract

The method of moments is used to study the electronic driving force for disorder to order transitions. Building on the moments foundation by introducing a mean-field approximation and a Landau-like order parameter, it is shown that ordering is energetically favorable for certain electron counts, minimizing the fourth moment of the crystal density of states. A straightforward method for calculating the moments to arbitrary order is presented, relying only on a knowledge of the low-temperature ordering pattern and a finite number of possible short-range ordering patterns. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
1995
Full Text
View/download PDF

58. Substitutional Growth of Methylammonium Lead Iodide Perovskites in Alcohols.

Author

Acik, Muge, Alam, Todd M., Guo, Fangmin, Ren, Yang, Lee, Byeongdu, Rosenberg, Richard A., Mitchell, John F., Park, In Kee, Lee, Geunsik, and Darling, Seth B.

Subjects
METHYLAMMONIUM, LEAD iodide, PEROVSKITE, ALCOHOLS (Chemical class), THERMAL stability
Abstract

Abstract: Methylammonium lead iodide (MAPbI3) perovskites are organic–inorganic semiconductors with long carrier diffusion lengths serving as the light‐harvesting component in optoelectronics. Through a substitutional growth of MAPbI3 catalyzed by polar protic alcohols, evidence is shown for their substrate‐ and annealing‐free production and use of toxic solvents and high temperature is prevented. The resulting variable‐sized crystals (≈100 nm–10 µm) are found to be tetragonally single‐phased in alcohols and precipitated as powders that are metallic‐lead‐free. A comparatively low MAPbI3 yield in toluene supports the role of alcohol polarity and the type of solvent (protic vs aprotic). The theoretical calculations suggest that overall Gibbs free energy in alcohols is lowered due to their catalytic impact. Based on this alcohol‐catalyzed approach, MAPbI3 is obtained, which is chemically stable in air up to ≈1.5 months and thermally stable (≤300 °C). This method is amendable to large‐scale manufacturing and ultimately can lead to energy‐efficient, low‐cost, and stable devices. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

59. Thickness-dependent properties of (110)-oriented La1.2Sr1.8Mn2O7 thin films.

Author

Takamura, Yayoi, Chopdekar, Rajesh V., Grepstad, Jostein K., Suzuki, Yuri, Marshall, Ann F., Vailionis, Arturas, Hong Zheng, and Mitchell, John F.

Subjects
THIN films, MAGNETICS, MAGNETISM, SEMICONDUCTORS, FERROMAGNETISM
Abstract

We have grown (110)-oriented thin films of the bilayer manganite La1.2Sr1.8Mn2O7 [n=2 phase of the Ruddlesden-Popper (RP) family] by pulsed laser deposition. The structural, magnetic, and magnetotransport properties of these films depend strongly on the growth conditions as well as the film thickness. Optimal growth conditions of 900 °C and 100 mTorr O2 balance the oxygenation of the n=2 phase without causing its decomposition into the n=1 and ∞ phases of the RP family. With increasing film thickness, the film evolves from a mixture of the n=1, 2, and ∞ phases to a film composed primarily of the n=2 phase. The thicker films possess bulklike properties with a ferromagnetic/paramagnetic transition that coincides with a resistivity maximum at a reduced Tc∼90 K (vs 120 K in bulk) and an anisotropy ratio, ρc/ρab∼20–200 over the temperature range 5–380 K. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

60. Infrastructure Strategy for the European Earth System Modelling Community 2012-2022

Author

Mitchell, John F, Budich, Reinhard, Joussaume, Sylvie, Lawrence, Bryan N, and Marotzke, Jochem

Subjects
ecology and environment, computer science, data and information
Abstract

This document explores the infrastructure needed during the next decade to support European climate research for seasonal to centennial climate predictions. This research will be integral to providing the scientific basis for climate services. It is highly relevant to the objectives of the Joint Programming Initiative on Climate "Connecting Climate Knowledge for Europe". The scientific community working on climate modelling is organized within the European Network for Earth System modelling (ENES). It has outlined major scientific issues both related to the reliability of climate change predictions and to the scientific understanding of climate natural variability. The document presents a vision of what could be available in 10 years time. It is envisaged that by the end of the decade, convective scales will be fully featured in climate models. Initialization and ensemble techniques will be well developed. Uncertainty will be well characterised ensuring appropriate diversity in both regional predictions and longer paleoclimatic simulations. It will be possible to initialise models from real data using full data assimilation techniques. It will be easier to evaluate models and their shorter range projections using hindcasts applied to real data, and such evaluation will be harnessed in a cycle of continuous model improvement. The implications of this vision for infrastructure are set out. The most demanding goal is to ensure by the end of the decade convective scales are resolved in European climate models of the Earth system with the objective to obtain regional climate predictions for next few decades which are more reliable. This in turn will require intensive and adapted access to exascale computing (1018 operations per second), co-located to an unusually large data archive, which needs to be connected to national archives by networks transferring data at rates faster than Tera bits/second. European models will benefit from being more modern in terms of flexibility and usability, and having a designed diversity, with the number of model «families» possibly reduced and commensurate with the resources available for their development and use.They should scale very well on high performance computers, but also allow usage across the whole computing pyramid. This will mandate a better connected and organized European community, agreeing and working together on common goals. The requirements to ensure the availability of appropriately skilled experts is outlined, and possible funding and governance are discussed. ENES recommends the following action items for the climate modelling research infrastructure: 1. Provide a blend of high-performance computing facilities ranging from national machines to a worldclass computing facility suitable for climate applications, which, given the workload anticipated, may well have to be dedicated to climate simulations. 2. Accelerate the preparation for exascale computing, e.g. by establishing closer links to PRACE and by developing new algorithms for massively parallel many-core computing. 3. Ensure data from climate simulations are easily available and well documented, especially for the climate impacts community. 4. Build a physical network connecting national archives with transfer capacities exceeding Tbits/sec. 5. Strengthen the European expertise in climate science and computing to enable the long term vision to be realized. Strengthening the European climate modelling infrastructure will provide Europe with the necessary evidence and expertise for its mitigation and adaptation policies., Previously curated at: http://cedadocs.ceda.ac.uk/1351/ The publish date on this item was its original published date. Associated projects: InfraStructure for the European Network for Earth System Modelling (IS-ENES) Main files in this record: enes_foresight.pdf Item originally deposited with Centre for Environmental Data Analysis (CEDA) document repository by Dr Graham Parton. Transferred to CEDA document repository community on Zenodo on 2022-11-24

Published
2012
Full Text
View/download PDF

61. Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3− δ.

Author

Wu, Xuewang, Walter, Jeff, Feng, Tianli, Zhu, Jie, Zheng, Hong, Mitchell, John F., Biškup, Neven, Varela, Maria, Ruan, Xiulin, Leighton, Chris, and Wang, Xiaojia

Subjects
THERMAL conductivity, EPITAXY, PHONONIC crystals, PIEZOELECTRICITY, STRONTIUM titanate
Abstract

Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity ( ΛLSCO) of epitaxial La0.5Sr0.5CoO3− δ (LSCO) of varying thickness (<20 nm) on LaAlO3 and SrTiO3 substrates. These LSCO films possess ordered oxygen vacancies as the primary means of lattice mismatch accommodation with the substrate, which induces compressive/tensile strain and thus controls the orientation of the oxygen vacancy ordering (OVO). TDTR results demonstrate that the room-temperature ΛLSCO of LSCO on both substrates (1.7 W m−1 K−1) are nearly a factor of four lower than that of bulk single-crystal LSCO (6.2 W m−1 K−1). Remarkably, this approaches the lower limit of amorphous oxides (e.g., 1.3 W m−1 K−1 for glass), with no dependence on the OVO orientation. Through theoretical simulations, origins of the glass-like thermal conductivity of LSCO are revealed as a combined effect resulting from oxygen vacancies (the dominant factor), Sr substitution, size effects, and the weak electron/phonon coupling within the LSCO film. The absence of OVO dependence in the measured ΛLSCO is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when δ is small; (2) the missing electronic contribution to ΛLSCO along the through-plane direction for these ultrathin LSCO films on insulating substrates. [ABSTRACT FROM AUTHOR]

Published
2017
Full Text
View/download PDF

62. Full bulk spin polarization and intrinsic tunnel barriers at the surface of layered manganites

Author

Freeland, John W., Gray, Kenneth E., Özyüzer, Lütfi, Berghuis, Peter, Badica, E., Kavich, Jerald J., Zheng, Hong, Mitchell, John F., TR5135, Özyüzer, Lütfi, and Izmir Institute of Technology. Physics

Subjects
Condensed Matter::Soft Condensed Matter, Quantitative Biology::Subcellular Processes, Physics::Biological Physics, Antiferromagnetism, Data reduction, Crystal structure, Condensed Matter::Strongly Correlated Electrons, Nanostructured materials, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Magnetization
Abstract

The affect of full bulk spin polarization and intrinsic tunnel barriers on the surface of layered manganites were studied using a combination of surface-sensitive x-ray and tunnelling process. The surface bilayer of air-cleaved layered manganites forms an antiferromagnetic insulating nanoskin composed of a single bilayer unit. It was shown that for the quasi-two-dimensional bilayer manganites the outermost Mn-O bilayer is affected while the next bilayer displays the full spin polarization of the bulk. The results show that the outermost bilayer act as an intrinsic barrier between the fully spin-polarized bilayer beneath and a subsequently deposited ferromagnetic counterelectrode., US Department of Energy (DOE), Basic Energy Sciences: W-31-109-ENG-38

Published
2005

84. Estimation of natural and anthropogenic contributions to twentieth century temperature change

Author

Tett, Simon F. B., primary, Jones, Gareth S., additional, Stott, Peter A., additional, Hill, David C., additional, Mitchell, John F. B., additional, Allen, Myles R., additional, Ingram, William J., additional, Johns, Tim C., additional, Johnson, Colin E., additional, Jones, Andy, additional, Roberts, David L., additional, Sexton, David M. H., additional, and Woodage, Margaret J., additional

Published
2002
Full Text
View/download PDF

86. Dedicated High-Resolution Powder Diffraction Beamline at the Advanced Photon Source.

Author

Lee, Peter L., Beno, Mark A., Shu, Deming, Ramanathan, Mohan, Mitchell, John F., Jorgensen, James D., Von Dreele, Robert B., and Warwick, T.

Subjects
OPTICAL diffraction, HIGH resolution spectroscopy, PHOTONS, SYNCHROTRONS, LIGHT sources, SPECTRUM analysis
Abstract

A high-resolution x-ray powder diffraction beamline that exploits the high flux, high energy resolution, and precise energy tuning of the third-generation synchrotron source will be built at the Advanced Photon Source (APS). The goal is to establish a high-resolution high-throughput dedicated powder instrument at the APS to serve the powder community. We describe design of the instrument that is able to measure a complete high-resolution powder pattern in one hour or less, uses automation to optimize throughput, has the ability to readily tune over a wide range of x-ray energies quickly and easily covering important absorption edges for resonant data measurements, and has the ability to accommodate various environmental devices for high-temperature, low-temperature or time-resolved data collection. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results