On the "Hirshleifer effect'' of unscheduled monetary policy announcements.

When monetary policy announcements are expected to occur at scheduled dates, the event of an unscheduled announcement often "surprises" financial markets. However, if the information provider knows the future policy beforehand, he might be induced to anticipate the release of information without waiting for the next scheduled date, on the assumption that better informed traders will be able to attain superior equilibria. On October 15,.1998, January 3 and April 18, 2001 the chairman of U.S. Fed announced a half point interest rate cut well before the next scheduled meeting. The real surprise for the markets was the timing, not the content, of the announcement. In this paper we look at the volume of trade in interest rate futures before these three dates and compare it to the volume of trade before scheduled meetings. We argue that the wrong timing of policy announcements might involve an "Hirshleifer effect" and prevent a significant volumes of securities to transact for hedging purposes.

Compacton formation under Allen--Cahn dynamics

We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We analytically solve the stationary problem and deduce the existence of so-called compactons, namely, connections on a finite interval between the two phases. The dynamics problem is numerically solved and compacton formation is described

Temperature-driven volume transition in hydrogels: phase--coexistence and interface localization

We study volume transition phenomenon in hydrogels within the framework of Flory-Rehner thermodynamic modelling; we show that starting from different models for the Flory parameter different conclusions can be achieved, in terms of admissible coexisting equilibria of the system. In particular, with explicit reference to a one-dimensional problem we establish the ranges of both temperature and traction which allow for the coexistence of a swollen and a shrunk phase. Through consideration of an augmented Flory-Rehner free-energy, which also accounts for the gradient of volume changes, we determine the position of the interface between the coexisting phases, and capture the connection profile between them

Kink Localization under Asymmetric Double-Well Potential

We study diffuse phase interfaces under asymmetric double-well potential energies with degenerate minima and demonstrate that the limiting sharp profile, for small interface energy cost, on a finite space interval is in general not symmetric and its position depends exclusively on the second derivatives of the potential energy at the two minima (phases). We discuss an application of the general result to porous media in the regime of solid-fluid segregation under an applied pressure and describe the interface between a fluid-rich and a fluid-poor phase. Asymmetric double-well potential energies are also relevant in a very different field of physics as that of Brownian motors. An intriguing analogy between our result and the direction of the dc soliton current in asymmetric substrate driven Brownian motors is pointed out

On the Galois Lattice of Bipartite Distance Hereditary Graphs

We give a complete characterization of bipartite graphs hav- ing tree-like Galois lattices. We prove that the poset obtained by deleting bottom and top elements from the Galois lattice of a bipartite graph is tree-like if and only if the graph is a Bipartite Distance Hereditary graph. We show that the lattice can be realized as the containment relation among directed paths in an arborescence. Moreover, a compact encoding of Bipartite Distance Hereditary graphs is proposed, that allows optimal time computation of neighborhood intersections and maximal bicliques

On Type II strings in exact superconformal non-constant RR backgrounds

An explicitly exact superconformal description is provided to some classes of Type II string theories in non constant RR backgrounds. This is done by applying the manifest (2,2) approach of Berkovits and Maldacena to Type II strings and by studying the condition of exact conformal invariance of certain supersymmetric backgrounds. We find a new set of exact type IIA strings with non constant RR 2-form and 4-form curvatures and for type IIB with non constant 3-form curvature.Comment: 15 pages; typos and a reference adde

Evaluation of MGIT 960 and the colorimetric-based method for tuberculosis drug susceptibility testing

SETTING: Dr Cetrángolo Hospital, Buenos Aires Province, Argentina. OBJECTIVE: Evaluation of the BACTEC? Mycobacteria Growth Indicator Tube (MGIT)? 960 system and the colorimetric-based method (CMM) for fi rst- and second line drug susceptibility testing (FL-DST, SL-DST) against Mycobacterium tuberculosis. DESIGN: FL-DST was studied using SIRE MGIT 960. Minimal inhibitory concentrations (MICs) for isoniazid (INH), streptomycin, rifampicin (RMP), ethambutol (EMB) and levofl oxacin (LVX) were also determined by CMM using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT). MICs for amikacin (AMK), kanamycin (KM), capreomycin (CPM), ethionamide (ETH), cycloserine, ofl oxacin (OFX), linezolide (LZ) and moxifl oxacin (MFX) were determined on 94 multidrug resistant M. tuberculosis isolates by MGIT 960 and CMM. Statistical methods were applied to define drug susceptible and drug-resistant isolates on the basis of the comparison between results obtained by gold standards. RESULTS: A total of 1626 clinical isolates were studied. Critical drug concentrations could be defi ned in less than 10 days for both CMM and MGIT 960. CMM was cheaper but more laborious than MGIT 960. The highest performances of both methods were achieved for AMK, RMP, OFX, LZ and MFX, followed by INH, ETH, KM, CPM and LVX (tested only by CMM). CONCLUSIONS: Both methods could be implemented as rapid diagnostic tools to detect drug-resistant isolates in clinical practice.Fil: Morcillo, N.. Provincia de Buenos Aires. Ministerio de Salud. Hospital "Dr. Antonio A. Cetrángolo"; ArgentinaFil: Imperiale, Belén Rocío. Provincia de Buenos Aires. Ministerio de Salud. Hospital "Dr. Antonio A. Cetrángolo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Di Giulio, B.. Provincia de Buenos Aires. Ministerio de Salud. Hospital "Dr. Antonio A. Cetrángolo"; Argentin

Stability of the stationary solutions of the Allen-Cahn equation with non-constant stiffness

We study the solutions of a generalized Allen-Cahn equation deduced from a Landau energy functional, endowed with a non-constant higher order stiffness. We assume the stiffness to be a positive function of the field and we discuss the stability of the stationary solutions proving both linear and local non-linear stability

Simulating noisy quantum protocols with quantum trajectories

The theory of quantum trajectories is applied to simulate the effects of quantum noise sources induced by the environment on quantum information protocols. We study two models that generalize single qubit noise channels like amplitude damping and phase flip to the many-qubit situation. We calculate the fidelity of quantum information transmission through a chaotic channel using the teleportation scheme with different environments. In this example, we analyze the role played by the kind of collective noise suffered by the quantum processor during its operation. We also investigate the stability of a quantum algorithm simulating the quantum dynamics of a paradigmatic model of chaos, the baker's map. Our results demonstrate that, using the quantum trajectories approach, we are able to simulate quantum protocols in the presence of noise and with large system sizes of more than 20 qubits.Comment: 11 pages, 7 fig