International Risk Sharing and the Choice of Exchange-Rate Regime

This paper examines the argument that the fixed exchange rate regime should be preferred to the flexible rate regime because the former allows risk sharing across countries while the latter does not. The analysis is performed in a two-country overlapping generations model, where markets are incomplete under either exchange regime. In this second best world, it is demonstrated that the ability to share risk across countries in the fixed rate regime does not necessarily lead to higher welfare than the inability to share risk in the flexible rate regime.

Orbital Floquet Engineering of Exchange Interactions in Magnetic Materials

We present a new scheme to control the spin exchange interactions between two magnetic ions by manipulating the orbital degrees of freedom using a periodic drive. We discuss two different protocols for orbital Floquet engineering. In one case, we modify the properties of the ligand orbitals which mediate magnetic interactions between two transition metal ions. While in the other case, we mix the d orbitals on each magnetic ion. In contrast to previous works on Floquet engineering of magnetic properties, the present scheme makes use of the AC Stark shift of the states involved in the exchange process

Hedge funds: an industry in its adolescence

The dramatic increase in the number of hedge funds and the "institutionalization" of the industry over the past decade have spurred rigorous research into hedge fund performance. This research has tended to uncover more questions than answers about the dynamic and multifaceted hedge fund industry. ; This article presents a simple hedge fund business model in which fund returns are a function of three key elements -- how the funds trade, where they trade, and how the positions are financed. The article also provides methods to help investors, intermediaries, and regulators identify systemic risk factors inherent in hedge fund strategies. ; Estimating these risk factors requires having an accurate history of hedge fund performance. The authors examine recent statistics from three commercial hedge fund databases and discuss the problems with database biases that must be recognized to obtain accurate measures of returns. ; While the data show that today's hedge funds use myriad strategies that have no uniform definition, the proposed business model implies that hedge fund managers are diversifying in order to maximize the enterprise value of their firms. But this diversification does not preclude the risk of leveraged opinions converging onto the same set of bets. Preventing convergence risk will require action by investors, intermediaries, regulators, and fund managers to improve industry-level disclosure and transparency while preserving the privacy of individual hedge funds' positions.Hedge funds

The Profitability of Currency Speculation

This paper presents the results of a post-sample simulation of a speculative strategy using a portfolio of foreign currency forward contracts.The main new features of the speculative strategy are (a)the use of Kalman filters to update the forecasting equation, (b) the allowance for transactions,costs and margin requirements and (c) the endogenous determination of the leveraging of the portfolio. While the forecasting model tended to overestimate profit and underestimate risk, the strategy was still profitable over a three year period and it was possible to reject the hypothesis that the sum of profits was zero. Furthermore, the currency portfolio was found to have an extremely low market risk. Combinations of the speculative currency portfolio with traditional portfolios of U.S. equities resulted in considerable improvements in risk-adjusted returns on capital.

Doping driven structural distortion in the bilayer iridate (Sr1−x_{1-x}Lax_x)3_3Ir2_2O7_7

Neutron single crystal diffraction and rotational anisotropy optical second harmonic generation data are presented resolving the nature of the structural distortion realized in electron-doped (Sr$_{1-x}$La$_x$)$_3$Ir$_2$O$_7$ with $x=0.035$ and $x=0.071$. Once electrons are introduced into the bilayer spin-orbit assisted Mott insulator Sr$_3$Ir$_2$O$_7$, previous studies have identified the appearance of a low temperature structural distortion and have suggested the presence of a competing electronic instability in the phase diagram of this material. Our measurements resolve a lowering of the structural symmetry from monoclinic $C2/c$ to monoclinic $P2_1/c$ and the creation of two unique Ir sites within the chemical unit cell as the lattice distorts below a critical temperature $T_S$. Details regarding the modifications to oxygen octahedral rotations and tilting through the transition are discussed as well as the evolution of the low temperature distorted lattice as a function of carrier substitution.Comment: 8 pages, 4 figure

PR-Set7 is Degraded in a Conditional Cul4A Transgenic Mouse Model of Lung Cancer.

BackgroundMaintenance of genomic integrity is essential to ensure normal organismal development and to prevent diseases such as cancer. PR-Set7 (also known as Set8) is a cell cycle regulated enzyme that catalyses monomethylation of histone 4 at Lys20 (H4K20me1) to promote chromosome condensation and prevent DNA damage. Recent studies show that CRL4CDT2-mediated ubiquitylation of PR-Set7 leads to its degradation during S phase and after DNA damage. This might occur to ensure appropriate changes in chromosome structure during the cell cycle or to preserve genome integrity after DNA damage.MethodsWe developed a new model of lung tumor development in mice harboring a conditionally expressed allele of Cul4A. We have therefore used a mouse model to demonstrate for the first time that Cul4A is oncogenic in vivo. With this model, staining of PR-Set7 in the preneoplastic and tumor lesions in AdenoCre-induced mouse lungs was performed. Meanwhile we identified higher protein level changes of γ-tubulin and pericentrin by IHC.ResultsThe level of PR-Set7 down-regulated in the preneoplastic and adenocarcinomous lesions following over-expression of Cul4A. We also identified higher levels of the proteins pericentrin and γ-tubulin in Cul4A mouse lungs induced by AdenoCre.ConclusionsPR-Set7 is a direct target of Cul4A for degradation and involved in the formation of lung tumors in the conditional Cul4A transgenic mouse model