964 research outputs found
Strategic Factors in Nineteenth Century American Economic History: A Volume to Honor Robert W. Fogel
Money versus Credit Rationing: Evidence for the National Banking Era, 1880-1914
In this paper we examine the evidence for two competing views of how monetary and financial disturbances influenced the real economy during the national banking era, 1880-1914. According to the monetarist view, monetary disturbances affected the real economy through changes on the liability side of the banking system's balance sheet independent of the composition of bank portfolios. According to the credit rationing view, equilibrium credit rationing in a world of asymmetric information can explain short-run fluctuations in real output. Using structural VARs we incorporate monetary variables in credit models and credit variables in monetarist models, with inconclusive results. To resolve this ambiguity, we invoke the institutional features of the national banking era. Most of the variation in bank loans is accounted for by loans secured by stock, which in turn reflect volatility in the stock market. When account is taken of the stock market, the influence of credit in the VAR model is greatly reduced, while the influence of money remains robust. The breakdown of the composition of bank loans into stock market loans (traded in open asset markets) and other business loans (a possible setting for credit rationing) reveals that other business loans remained remarkably stable over the business cycle.
Phase diagram of the Kondo necklace: a mean-field renormalization group approach
In this paper we investigate the magnetic properties of heavy fermions in the
antiferromagnetic and dense Kondo phases in the framework of the Kondo necklace
model. We use a mean field renormalization group approach to obtain a
temperature versus Kondo coupling phase diagram for this model in
qualitative agreement with Doniach's diagram, proposed on physical grounds. We
further analyze the magnetically disordered phase using a two-sites approach.
We calculate the correlation functions and the magnetic susceptibility that
allow to identify the crossover between the spin-liquid and the local moment
regimes, which occurs at a {\em coherence} temperature.Comment: 5 figure
Intrafirm trade and vertical fragmentation in U.S.multinational corporations
Using firm-level data, we document two new facts regarding intrafirm trade and the activities of the foreign affiliates of U.S. multinational corporations. First, intrafirm trade is concentrated among a small number of large affiliates within large multinational corporations; the median affiliate ships nothing to the rest of the corporation. Second, we find that the input-output coefficient linking the parent’s and affiliate’s industries of operation—a characteristic commonly associated with production fragmentation— is not related to a corresponding intrafirm low of goods
The proximity-concentration tradeoff under uncertainty
In this article, we analyse the firm's choice between serving a foreign market through exports or through foreign affiliate sales in an environment characterized by country-specific shocks to the cost of production. Our model predicts that country pairs with less-correlated output fluctuations trade more, relative to affiliate sales, whereas countries with more-volatile fluctuations are served relatively more by exporters than by foreign affiliates selling abroad. Using detailed data on trade and affiliate sales, we find empirical support for our model's predictions
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Tracing diagnosis trajectories over millions of patients reveal an unexpected risk in schizophrenia.
The identification of novel disease associations using big-data for patient care has had limited success. In this study, we created a longitudinal disease network of traced readmissions (disease trajectories), merging data from over 10.4 million inpatients through the Healthcare Cost and Utilization Project, which allowed the representation of disease progression mapping over 300 diseases. From these disease trajectories, we discovered an interesting association between schizophrenia and rhabdomyolysis, a rare muscle disease (incidence < 1E-04) (relative risk, 2.21 [1.80-2.71, confidence interval = 0.95], P-value 9.54E-15). We validated this association by using independent electronic medical records from over 830,000 patients at the University of California, San Francisco (UCSF) medical center. A case review of 29 rhabdomyolysis incidents in schizophrenia patients at UCSF demonstrated that 62% are idiopathic, without the use of any drug known to lead to this adverse event, suggesting a warning to physicians to watch for this unexpected risk of schizophrenia. Large-scale analysis of disease trajectories can help physicians understand potential sequential events in their patients
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Complex Chemical Reaction Networks from Heuristics-Aided Quantum Chemistry
While structures and reactivities of many small molecules can be computed efficiently and accurately using quantum chemical methods, heuristic approaches remain essential for modeling complex structures and large-scale chemical systems. Here, we present a heuristics-aided quantum chemical methodology applicable to complex chemical reaction networks such as those arising in cell metabolism and prebiotic chemistry. Chemical heuristics offer an expedient way of traversing high-dimensional reactive potential energy surfaces and are combined here with quantum chemical structure optimizations, which yield the structures and energies of the reaction intermediates and products. Application of heuristics-aided quantum chemical methodology to the formose reaction reproduces the experimentally observed reaction products, major reaction pathways, and autocatalytic cycles.Chemistry and Chemical BiologyPhysic
Regulation of fibroblast growth factor receptor signalling and trafficking by Src and Eps8
Fibroblast growth factor receptors (FGFRs) mediate a wide spectrum of cellular responses that are crucial for development and wound healing. However, aberrant FGFR activity leads to cancer. Activated growth factor receptors undergo stimulated endocytosis, but can continue to signal along the endocytic pathway. Endocytic trafficking controls the duration and intensity of signalling, and growth factor receptor signalling can lead to modifications of trafficking pathways. We have developed live-cell imaging methods for studying FGFR dynamics to investigate mechanisms that coordinate the interplay between receptor trafficking and signal transduction. Activated FGFR enters the cell following recruitment to pre-formed clathrin-coated pits (CCPs). However, FGFR activation stimulates clathrin-mediated endocytosis; FGF treatment increases the number of CCPs, including those undergoing endocytosis, and this effect is mediated by Src and its phosphorylation target Eps8. Eps8 interacts with the clathrin-mediated endocytosis machinery and depletion of Eps8 inhibits FGFR trafficking and immediate Erk signalling. Once internalized, FGFR passes through peripheral early endosomes en route to recycling and degredative compartments, through an Src- and Eps8-dependent mechanism. Thus Eps8 functions as a key coordinator in the interplay between FGFR signalling and trafficking. This work provides the first detailed mechanistic analysis of growth factor receptor clustering at the cell surface through signal transduction and endocytic trafficking. As we have characterised the Src target Eps8 as a key regulator of FGFR signalling and trafficking, and identified the early endocytic system as the site of Eps8-mediated effects, this work provides novel mechanistic insight into the reciprocal regulation of growth factor receptor signalling and trafficking
Zero- and one-dimensional magnetic traps for quasi-particles
We investigate the possibility of trapping quasi-particles possessing spin
degree of freedom in hybrid structures. The hybrid system we are considering
here is composed of a semi-magnetic quantum well placed a few nanometers below
a ferromagnetic micromagnet. We are interested in two different micromagnet
shapes: cylindrical (micro-disk) and rectangular geometry. We show that in the
case of a micro-disk, the spin object is localized in all three directions and
therefore zero-dimensional states are created, and in the case of an elongated
rectangular micromagnet, the quasi-particles can move freely in one direction,
hence one-dimensional states are formed. After calculating profiles of the
magnetic field produced by the micromagnets, we analyze in detail the possible
light absorption spectrum for different micromagnet thicknesses, and different
distances between the micromagnet and the semimagnetic quantum well. We find
that the discrete spectrum of the localized states can be detected via
spatially-resolved low temperature optical measurement.Comment: 15 pages, 9 figure
Experimental observation of quantum entanglement in low dimensional spin systems
We report macroscopic magnetic measurements carried out in order to detect
and characterize field-induced quantum entanglement in low dimensional spin
systems. We analyze the pyroborate MgMnB_2O_5 and the and the warwickite
MgTiOBO_3, systems with spin 5/2 and 1/2 respectively. By using the magnetic
susceptibility as an entanglement witness we are able to quantify entanglement
as a function of temperature and magnetic field. In addition, we experimentally
distinguish for the first time a random singlet phase from a Griffiths phase.
This analysis opens the possibility of a more detailed characterization of low
dimensional materials
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