462 research outputs found
Hydrographic Surveying in the Great Lakes During the Nineteenth Century
This paper reviews the development of hydrographic surveys in the Great Lakes during the 19th century. It traces the work of the early Admiralty surveyors and of the U.S. Corps of Engineers through to the formation of the Canadian Hydrographic Service and describes some of the methods used and the hardships faced by the early surveyors
An archival case study : revisiting the life and political economy of Lauchlin Currie
This paper forms part of a wider project to show the significance of archival material on distinguished economists, in this case Lauchlin Currie (1902-93), who studied and taught at Harvard before entering government service at the US Treasury and Federal Reserve Board as the intellectual leader of Roosevelt's New Deal, 1934-39, as FDR's White House economic adviser in peace and war, 1939-45, and as a post-war development economist. It discusses the uses made of the written and oral material available when the author was writing his intellectual biography of Currie (Duke University Press 1990) while Currie was still alive, and the significance of the material that has come to light after Currie's death
Three variants of endogenous growth : as applied to the United Kingdom, 1948-2000
Paper focusing on the three variants of endogenous growth as applied to the United Kingdom from 1948-2000. The new growth theory, which took off with Romer (1986, 1987) and Lucas (1988) reemphasises the role of saving and capital accumulation in growth. In this theory technical change is made endogenous9 by making the production function yield increasing returns to scale rather than the neoclassical constant returns to scale. The result is that the contribution of inputs such as capital to growth is greater than in the conventional neoclassical models. Further, the ability of firms to devote more resources to new research10 is linked to some form of market power. In this context the role of such factors as patents, monopolistic competition and protectionism in making possible increased resources for new research are emphasised
Modelling stratospheric polar ozone using objective analysis
We have studied the development of the austral ozone hole using a 3-D spectral chemical transport model at R15 resolution for the period 15th September to 15th October, 1991. The model is driven by objectively analyzed wind fields obtained from the Canadian Meteorological Center and uses the chemical module developed by Kaminski (1992). Although extensive processing of NO(y) and Cl(x) occurs within the model, the ozone hole that develops appears shallow and ephemeral. Analysis of the results indicate that the meridional transport of ozone is sufficient to overwhelm the substantial chemical depletion that does occur. We suggest that the low resolution objectively analyzed data used is unable to capture the essential isolated nature of the vortex
Optical evidence of surface state suppression in Bi based topological insulators
A key challenge in condensed matter research is the optimization of
topological insulator (TI) compounds for the study and future application of
their unique surface states. Truly insulating bulk states would allow the
exploitation of predicted surface state properties, such as protection from
backscattering, dissipationless spin-polarized currents, and the emergence of
novel particles. Towards this end, major progress was recently made with the
introduction of highly resistive BiTeSe, in which surface state
conductance and quantum oscillations are observed at low temperatures.
Nevertheless, an unresolved and pivotal question remains: while room
temperature ARPES studies reveal clear evidence of TI surface states, their
observation in transport experiments is limited to low temperatures. A better
understanding of this surface state suppression at elevated temperatures is of
fundamental interest, and crucial for pushing the boundary of device
applications towards room-temperature operation. In this work, we
simultaneously measure TI bulk and surface states via temperature dependent
optical spectroscopy, in conjunction with transport and ARPES measurements. We
find evidence of coherent surface state transport at low temperatures, and
propose that phonon mediated coupling between bulk and surface states
suppresses surface conductance as temperature rises.Comment: 13 pages, 10 figure
New evidence on Allyn Young's style and influence as a teacher
This paper publishes the hitherto unpublished correspondence between Allyn Abbott Young's biographer Charles Blitch and 17 of Young's former students or associates. Together with related biographical and archival material, the paper shows the way in which this adds to our knowledge of Young's considerable influence as a teacher upon some of the twentieth century's greatest economists. The correspondents are as follows: James W Angell, Colin Clark, Arthur H Cole, Lauchlin Currie, Melvin G de Chazeau, Eleanor Lansing Dulles, Howard S Ellis, Frank W Fetter, Earl J Hamilton, Seymour S Harris, Richard S Howey, Nicholas Kaldor, Melvin M Knight, Bertil Ohlin, Geoffrey Shepherd, Overton H Taylor, and Gilbert Walker
FAK acts as a suppressor of RTK-MAP kinase signalling in Drosophila melanogaster epithelia and human cancer cells
Receptor Tyrosine Kinases (RTKs) and Focal Adhesion Kinase (FAK) regulate multiple signalling pathways, including mitogen-activated protein (MAP) kinase pathway. FAK interacts with several RTKs but little is known about how FAK regulates their downstream signalling. Here we investigated how FAK regulates signalling resulting from the overexpression of the RTKs RET and EGFR. FAK suppressed RTKs signalling in Drosophila melanogaster epithelia by impairing MAPK pathway. This regulation was also observed in MDA-MB-231 human breast cancer cells, suggesting it is a conserved phenomenon in humans. Mechanistically, FAK reduced receptor recycling into the plasma membrane, which resulted in lower MAPK activation. Conversely, increasing the membrane pool of the receptor increased MAPK pathway signalling. FAK is widely considered as a therapeutic target in cancer biology; however, it also has tumour suppressor properties in some contexts. Therefore, the FAK-mediated negative regulation of RTK/MAPK signalling described here may have potential implications in the designing of therapy strategies for RTK-driven tumours
Fermionic response from fractionalization in an insulating two-dimensional magnet
Conventionally ordered magnets possess bosonic elementary excitations, called
magnons. By contrast, no magnetic insulators in more than one dimension are
known whose excitations are not bosons but fermions. Theoretically, some
quantum spin liquids (QSLs) -- new topological phases which can occur when
quantum fluctuations preclude an ordered state -- are known to exhibit Majorana
fermions as quasiparticles arising from fractionalization of spins. Alas,
despite much searching, their experimental observation remains elusive. Here,
we show that fermionic excitations are remarkably directly evident in
experimental Raman scattering data across a broad energy and temperature range
in the two-dimensional material -RuCl. This shows the importance of
magnetic materials as hosts of Majorana fermions. In turn, this first
systematic evaluation of the dynamics of a QSL at finite temperature emphasizes
the role of excited states for detecting such exotic properties associated with
otherwise hard-to-identify topological QSLs.Comment: 5 pages, 3 figure
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