Mixed Signals Among Tests for Panel Cointegration

In this paper, we study the effect that different serial correlation adjustment methods can have on panel cointegration testing. As an example, we consider the very popular tests developed by Pedroni (1999, 2004). Results based on both simulated and real data suggest that different adjustment methods can lead to significant variations in test outcome, and thus also in the conclusions.Panel Data; Cointegration Testing; Parametric and Semiparametric Methods

Panel Cointegration and the Monetary Exchange Rate Model

This paper re-examines the validity of the monetary exchange rate model during the post-Bretton Woods era for 18 OECD countries. Our analysis simultaneously considers the presence of both cross-sectional dependence and multiple structural breaks, which have not received much attention in previous studies of the monetary model. The empirical results indicate that the monetary model emerges only when the presence of structural breaks and cross-country dependence has been taken into account. Evidence is also provided suggesting that the breaks in the monetary model can be derived from the underlying purchasing power parity relation.

A Rich Population of X-ray Emitting Wolf-Rayet Stars in the Galactic Starburst Cluster Westerlund 1

Recent optical and IR studies have revealed that the heavily-reddened starburst cluster Westerlund 1 (Wd 1) contains at least 22 Wolf-Rayet (WR) stars, comprising the richest WR population of any galactic cluster. We present results of a senstive Chandra X-ray observation of Wd 1 which detected 12 of the 22 known WR stars and the mysterious emission line star W9. The fraction of detected WN stars is nearly identical to that of WC stars. The WN stars WR-A and WR-B as well as W9 are exceptionally luminous in X-rays and have similar hard heavily-absorbed spectra with strong Si XIII and S XV emission lines. The luminous high-temperature X-ray emission of these three stars is characteristic of colliding wind binary systems but their binary status remains to be determined. Spectral fits of the X-ray bright sources WR-A and W9 with isothermal plane-parallel shock models require high absorption column densities log N$_{H}$ = 22.56 (cm$^{-2}$) and yield characteristic shock temperatures kT_shock ~ 3 keV (T ~ 35 MK).Comment: ApJL, 2006, in press (3 figures, 1 table

Improving Pasture Productivity and Persistence by Renovating or Rejuvenating

Forages make up a large part of the feed requirements of beef cattle, and grazing remains the most economical form of feed delivery. However, several years after pasture establishment, forage productivity and longevity usually decline. Maintaining productive forage stands in the long term becomes a major challenge that beef producers face. A 3-yr on-farm study was conducted to determine the comparative effects of several pasture rejuvenation methods, such as spraying of herbicides to control weeds and brush, Spray herbicide + direct seed in spring (RSS), forage seeding methods, fertilizer application (FERT), and pasture rest as well as aeration/spiking in fall (AF) and aeration/spiking in spring (AS) on forage dry matter (DM) yield and forage quality. Breaking & reseeding (B&R), which is a grassland renovation method, was compared to these four pasture rejuvenation methods. A no treatment method (control) was included for comparison. Three years after treatments were implemented, pasture rejuvenation methods did significantly affect (P\u3c 0.05) grass botanical composition but did not significantly influence (P\u3e 0.05) total DM yield and legume botanical composition. The only method that involved land cultivation and reseeding (B&R) showed higher total input costs than other methods. Overall, RSS as well as AS, AF and FERT had greater 2-year total forage production, revenue and returns, and profit over control than the other treatment methods

Hairpins in the conformations of a confined polymer

If a semiflexible polymer confined to a narrow channel bends around by 180 degrees, the polymer is said to exhibit a hairpin. The equilibrium extension statistics of the confined polymer are well understood when hairpins are vanishingly rare or when they are plentiful. Here we analyze the extension statistics in the intermediate situation via experiments with DNA coated by the protein RecA, which enhances the stiffness of the DNA molecule by approximately one order of magnitude. We find that the extension distribution is highly non-Gaussian, in good agreement with Monte Carlo simulations of confined discrete wormlike chains. We develop a simple model that qualitatively explains the form of the extension distribution. The model shows that the tail of the distribution at short extensions is determined by conformations with one hairpin.Comment: Revised version. 22 pages, 7 figures, 2 tables, supplementary materia

Modulation of Face-sensitive Event-related Potentials by Canonical and Distorted Human Faces: The Role of Vertical Symmetry and Up-Down Featural Arrangement

The study examined the sensitivity of early face-sensitive ERP components to the disruption of two structural properties embedded in faces, namely up-down featural arrangement and vertical asymmetry. Response times and ERPs were recorded as adults made an orientation judgment on canonical faces and distorted faces that had been manipulated for either or both of the mentioned properties. The P1, the N170 and the VPP allexhibited a similar linear increase in amplitude or latency as the properties were disrupted in the order of 1) up-down featural arrangement, 2) vertical symmetry, and 3) both up-down featural arrangement and vertical symmetry. Exceptions to this finding were seen for the amplitudes of the N170 and VPP, which were larger for the stimulus in which vertical symmetry was disrupted. Interestingly, the enhanced amplitudes of the N170 and VPP are consistent with impaired behavioral performance on the orientation judgment observed for this stimulus