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  • 1
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    African pastoralism: genetic imprints of origins and migrations (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-04-16
    Description: The genetic history of African cattle pastoralism is controversial and poorly understood. We reveal the genetic signatures of its origins, secondary movements, and differentiation through the study of 15 microsatellite loci in 50 indigenous cattle breeds spanning the present cattle distribution in Africa. The earliest cattle originated within the African continent, but Near East and European genetic influences are also identified. The initial expansion of African Bos taurus was likely from a single region of origin. It reached the southern part of the continent by following an eastern route rather than a western one. The B. indicus genetic influence shows a major entry point through the Horn and the East Coast of Africa and two modes of introgression into the continent.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hanotte, Olivier -- Bradley, Daniel G -- Ochieng, Joel W -- Verjee, Yasmin -- Hill, Emmeline W -- Rege, J Edward O -- New York, N.Y. -- Science. 2002 Apr 12;296(5566):336-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉International Livestock Research Institute, Post Office Box 30709, Nairobi, Kenya. o.hanotte@cgiar.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11951043" target="_blank"〉PubMed〈/a〉
    Keywords: Africa ; Alleles ; Analysis of Variance ; *Animal Husbandry ; Animals ; Animals, Domestic/classification/*genetics ; Archaeology ; Cattle/classification/*genetics ; Europe ; Genetic Variation ; *Genetics, Population ; Humans ; Microsatellite Repeats ; Middle East ; Principal Component Analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Proton transport through one-atom-thick crystals (2014)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2014-12-04
    Description: Graphene is increasingly explored as a possible platform for developing novel separation technologies. This interest has arisen because it is a maximally thin membrane that, once perforated with atomic accuracy, may allow ultrafast and highly selective sieving of gases, liquids, dissolved ions and other species of interest. However, a perfect graphene monolayer is impermeable to all atoms and molecules under ambient conditions: even hydrogen, the smallest of atoms, is expected to take billions of years to penetrate graphene's dense electronic cloud. Only accelerated atoms possess the kinetic energy required to do this. The same behaviour might reasonably be expected in the case of other atomically thin crystals. Here we report transport and mass spectroscopy measurements which establish that monolayers of graphene and hexagonal boron nitride (hBN) are highly permeable to thermal protons under ambient conditions, whereas no proton transport is detected for thicker crystals such as monolayer molybdenum disulphide, bilayer graphene or multilayer hBN. Protons present an intermediate case between electrons (which can tunnel easily through atomically thin barriers) and atoms, yet our measured transport rates are unexpectedly high and raise fundamental questions about the details of the transport process. We see the highest room-temperature proton conductivity with monolayer hBN, for which we measure a resistivity to proton flow of about 10 Omega cm(2) and a low activation energy of about 0.3 electronvolts. At higher temperatures, hBN is outperformed by graphene, the resistivity of which is estimated to fall below 10(-3) Omega cm(2) above 250 degrees Celsius. Proton transport can be further enhanced by decorating the graphene and hBN membranes with catalytic metal nanoparticles. The high, selective proton conductivity and stability make one-atom-thick crystals promising candidates for use in many hydrogen-based technologies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hu, S -- Lozada-Hidalgo, M -- Wang, F C -- Mishchenko, A -- Schedin, F -- Nair, R R -- Hill, E W -- Boukhvalov, D W -- Katsnelson, M I -- Dryfe, R A W -- Grigorieva, I V -- Wu, H A -- Geim, A K -- England -- Nature. 2014 Dec 11;516(7530):227-30. doi: 10.1038/nature14015. Epub 2014 Nov 26.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK [2] Manchester Centre for Mesoscience and Nanotechnology, The University of Manchester, Manchester M13 9PL, UK. ; School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK. ; Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China. ; Manchester Centre for Mesoscience and Nanotechnology, The University of Manchester, Manchester M13 9PL, UK. ; Institute for Molecules and Materials, Radboud University of Nijmegen, 6525 AJ Nijmegen, The Netherlands. ; School of Chemistry, The University of Manchester, Manchester M13 9PL, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25470058" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Chaotic Dirac billiard in graphene quantum dots (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-04-19
    Description: The exceptional electronic properties of graphene, with its charge carriers mimicking relativistic quantum particles and its formidable potential in various applications, have ensured a rapid growth of interest in this new material. We report on electron transport in quantum dot devices carved entirely from graphene. At large sizes (〉100 nanometers), they behave as conventional single-electron transistors, exhibiting periodic Coulomb blockade peaks. For quantum dots smaller than 100 nanometers, the peaks become strongly nonperiodic, indicating a major contribution of quantum confinement. Random peak spacing and its statistics are well described by the theory of chaotic neutrino billiards. Short constrictions of only a few nanometers in width remain conductive and reveal a confinement gap of up to 0.5 electron volt, demonstrating the possibility of molecular-scale electronics based on graphene.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ponomarenko, L A -- Schedin, F -- Katsnelson, M I -- Yang, R -- Hill, E W -- Novoselov, K S -- Geim, A K -- New York, N.Y. -- Science. 2008 Apr 18;320(5874):356-8. doi: 10.1126/science.1154663.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Manchester Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18420930" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Genome sequence, comparative analysis, and population genetics of the domestic horse (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-11-07
    Description: We report a high-quality draft sequence of the genome of the horse (Equus caballus). The genome is relatively repetitive but has little segmental duplication. Chromosomes appear to have undergone few historical rearrangements: 53% of equine chromosomes show conserved synteny to a single human chromosome. Equine chromosome 11 is shown to have an evolutionary new centromere devoid of centromeric satellite DNA, suggesting that centromeric function may arise before satellite repeat accumulation. Linkage disequilibrium, showing the influences of early domestication of large herds of female horses, is intermediate in length between dog and human, and there is long-range haplotype sharing among breeds.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785132/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785132/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wade, C M -- Giulotto, E -- Sigurdsson, S -- Zoli, M -- Gnerre, S -- Imsland, F -- Lear, T L -- Adelson, D L -- Bailey, E -- Bellone, R R -- Blocker, H -- Distl, O -- Edgar, R C -- Garber, M -- Leeb, T -- Mauceli, E -- MacLeod, J N -- Penedo, M C T -- Raison, J M -- Sharpe, T -- Vogel, J -- Andersson, L -- Antczak, D F -- Biagi, T -- Binns, M M -- Chowdhary, B P -- Coleman, S J -- Della Valle, G -- Fryc, S -- Guerin, G -- Hasegawa, T -- Hill, E W -- Jurka, J -- Kiialainen, A -- Lindgren, G -- Liu, J -- Magnani, E -- Mickelson, J R -- Murray, J -- Nergadze, S G -- Onofrio, R -- Pedroni, S -- Piras, M F -- Raudsepp, T -- Rocchi, M -- Roed, K H -- Ryder, O A -- Searle, S -- Skow, L -- Swinburne, J E -- Syvanen, A C -- Tozaki, T -- Valberg, S J -- Vaudin, M -- White, J R -- Zody, M C -- Broad Institute Genome Sequencing Platform -- Broad Institute Whole Genome Assembly Team -- Lander, E S -- Lindblad-Toh, K -- 098051/Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 2009 Nov 6;326(5954):865-7. doi: 10.1126/science.1178158.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA. c.wade@usyd.edu.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19892987" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Animals, Domestic/genetics ; Centromere/genetics ; Chromosome Mapping ; Chromosomes, Mammalian/*genetics ; Computational Biology ; DNA Copy Number Variations ; Dogs ; Evolution, Molecular ; Female ; Genes ; *Genome ; Haplotypes ; Horses/*genetics ; Humans ; Molecular Sequence Data ; Phylogeny ; Repetitive Sequences, Nucleic Acid ; *Sequence Analysis, DNA ; Synteny
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of deposition process on the magnetic properties of coupled permalloy thin films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6365-6367 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double layer thin films of permalloy (layer thickness 200–1300 A(ring)) with tantalum (50 A(ring)) as a nonmagnetic spacer have been prepared by e-beam evaporation. The effect of deposition parameters, especially the substrate temperature on the magnetic properties of these films has been examined. The coercivity(Hc) of the double layer films was found to be very sensitive to the substrate temperature in the permalloy layer thickness range of 200–600 A(ring). The coercivity of the films deposited at 40 °C is lower than at 300 °C and is almost independent of the Permalloy layer thickness. The XRD patterns and STM images of these two films exhibit large differences in permalloy grain size and grain orientation. However, the Hc of the single layer films deposited under the same conditions as the double layer films shows no significant change in this thickness region. The results indicate that the change of interface condition is primarily responsible for the Hc variation in the coupled films deposited at different substrate temperatures and strongly suggest that interface roughness plays a dominant role in the coupling between the permalloy layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352650
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  • 6
    Electronic Resource
    Electronic Resource
    The role of dipole coupling in multilayers : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5978-5980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work considers the role of magnetic dipole coupling in multilayers typically comprising a ferromagnetic material separated by a nonmagnetic metal spacer, e.g., NiFe/Ta. It has been suggested previously that dipolar fields may play an important role in the coupling of magnetic layers through a nonmagnetic spacer, in particular where surface roughness at the interface is significant. This work considers a first-order calculation of the dipole coupling energy and magnetic field between two adjacent layers. It is shown that dipole coupling energies originating from surface corrugations can behave in the same manner as a coercive field in terms of dependence on nonmagnetic spacer thickness and the degree of roughness. Interestingly, calculations also show that both ferromagnetic- and antiferromagnetic-like coupling can be explained in terms of this model. The role of the spacer thickness, magnetic layer thickness, and the form of the roughness is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353489
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  • 7
    Electronic Resource
    Electronic Resource
    Barkhausen transitions in single layer and bilayer thin permalloy films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6997-6999 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low coercivity of uniaxial thin nickel-iron multilayer films, prepared according to E. W. Hill, J. P. Li, and J. K. Birtwistle [J. Appl. Phys. 69, 4526 (1991)], makes them attractive for magnetic sensor applications. Barkhausen jumps, causing noise, limit the performance of such sensors. It has been reported [R. F. Soohoo, J. Appl. Phys. 69, 5871 (1991)] that, for any given sample under identical initial conditions, these Barkhausen jumps are deterministic rather than noisy in nature. This is consistent with the fact that the defect structure of a given sample is deterministic. This study compares power spectra and coercivity distributions from Barkhausen pulses obtained by applying varying alternating fields to thin permalloy films. The effect of an orthogonal bias field is also examined. The samples under examination consist of both single layer and bilayer films, produced as continuous layers by vacuum evaporation and ion milled into 40 mm diameter discs. The permalloy is of 80/20 composition and has a total thickness of 100 nm. The bilayer films have a nonmagnetic tantalum interlayer of thickness 5 nm. The rate of change of the applied field was varied between 2918.4 and 11.4 Oe/s, at an initial amplitude of 90 Oe. The results show that the Barkhausen pulses have a strong deterministic trend, but also contain a smaller nondeterministic component. As the frequency and amplitude are decreased, this random effect becomes larger. As might be expected when an orthogonal bias field is applied to the samples, the amplitudes of the pulses are decreased. The films also exhibit a corresponding reduction in coercivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356755
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetization distributions in thin film Permalloy strips : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5862-5864 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin film Permalloy strips are used extensively for magnetoresistive sensors both in magnetometry and magnetic recording. A determination of magnetization distributions is vital to allow optimization of sensor performance. Results from a previously described scanning laser microscope (SLM) unambiguously determine magnetization distributions to submicron resolution. Operating the SLM in a mode sensitive to magnetization angles about the long axis of the strip shows typical closure domains. If the mode is sensitive to fluctuations about the strip short axis then light and dark bands are observed. These results indicate that the magnetization is not parallel with the strip edges within the domains as normally considered for closure domains. The SLM images are compared with results from a previously described numerical micromagnetic model. Results from the model compare well with those from the SLM, confirming the ability of the model to reliably predict domain activity in Permalloy strips. Results are shown for Permalloy strips of approximately 15 μm×50 μm and 250 A(ring) thick in the presence of dc and ac magnetic fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347849
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of pinning magnetization with geometrical features in thin permalloy films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6519-6521 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work considers the use of geometric alterations to the edges of a strip of thin magnetoresistive material used to make a magnetometer device. The geometric features in the form of narrow fins are intended to improve the performance of the device by pinning the magnetization at the strip edges at an angle corresponding to the high sensitivity region of the magnetoresistance curve, thus including this region in the contribution to total resistance change. Both theoretical calculations using a micromagnetic model and experimental work on a prototype device are described. Results show that the device behaves closely to the modeling predictions, exhibiting a large sensitivity of 17 μV/V/μT, 70% greater than a more conventional device, with the additional capability of a trimmable orthogonal field rejection. Differences between the predicted and measured devices are described in terms of the shortcomings of the model and to domain activity in the device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352600
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic and structural properties of permalloy-tantalum multilayer thin films : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4526-4528 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work describes a detailed investigation into the magnetic and structural properties of permalloy-tantalum multilayered thin films produced by vacuum evaporation. Their microstructure was investigated using high-resolution TEM and the magnetic properties were measured with vibrating-sample and vibrating-reed magnetometers. The results show a reduction in coercivity for the multilayer films which is independent of the number of layers but depends strongly on the magnetic layer thickness. The tantalum layer is shown to be continuous and microcrystalline down to 25-A(ring) thickness, but the interface between the layers is irregular and may give rise to additional magnetostatic coupling as the tantalum layer thickness is reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348348
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