A Threshold Model of Real US GDP and the Problem of Constructing Confidence Intervals in TAR Models

We estimate real U.S. GDP growth as a threshold autoregressive process, and construct confidence intervals for the parameter estimates. However, there are various approaches that can be used in constructing the confidence intervals. Specifically, standard- t , bootstrap- t , and bootstrap-percentile confidence intervals are simulated for the slope coefficients and the estimated threshold. However, the results for the different methods have very different economic implications. We perform a Monte Carlo experiment to evaluate the various methods.Bootstrap GDP; Threshold Autoregression; Bootstrap Confidence Intervals

Reflectionless Tunnelling of Light in Gradient Optics

We analyse the optical (or microwave) tunnelling properties of electromagnetic waves passing through thin films presenting a specific index profile providing a cut-off frequency, when they are used below this frequency. We show that contrary to the usual case of a square index profile, where tunnelling is accompanied with a strong attenuation of the wave due to reflection, such films present the possibility of a reflectionless tunnelling, where the incoming intensity is totally transmitted

On a counterexample to a conjecture by Blackadar

Blackadar conjectured that if we have a split short-exact sequence 0 -> I -> A -> A/I -> 0 where I is semiprojective and A/I is isomorphic to the complex numbers, then A must be semiprojective. Eilers and Katsura have found a counterexample to this conjecture. Presumably Blackadar asked that the extension be split to make it more likely that semiprojectivity of I would imply semiprojectivity of A. But oddly enough, in all the counterexamples of Eilers and Katsura the quotient map from A to A/I is split. We will show how to modify their examples to find a non-semiprojective C*-algebra B with a semiprojective ideal J such that B/J is the complex numbers and the quotient map does not split.Comment: 6 page

Single Proton Knock-Out Reactions from 24,25,26F

The cross sections of the single proton knock-out reactions from 24F, 25F, and 26F on a 12C target were measured at energies of about 50 MeV/nucleon. Ground state populations of 6.6+-.9 mb, 3.8+-0.6 mb for the reactions 12C(24F,23O) and 12C(25F,24O) were extracted, respectively. The data were compared to calculations based on the many-body shell model and the eikonal theory. In the reaction 12C(26F,25O) the particle instability of 25O was confirmed

Asymmetric Conditional Volatility in International Stock Markets

Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the S&P 500, FTSE100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.Comment: 11 pages, 3 figure

One-neutron knockout from 57^{57}Ni

The single-particle structure of $^{57}$Ni and level structure of $^{56}$Ni were investigated with the \mbox{$^{9}$Be ($^{57}$Ni,$^{56}$Ni+$\gamma$)$\it{X}$} reaction at 73 MeV/nucleon. An inclusive cross section of 41.4(12) mb was obtained for the reaction, compared to a theoretical prediction of 85.4 mb, hence only 48(2)% of the theoretical cross section is exhausted. This reduction in the observed spectroscopic strength is consistent with that found for lighter well-bound nuclei. One-neutron removal spectroscopic factors of 0.58(11) to the ground state and 3.7(2) to all excited states of $^{56}$Ni were deduced.Comment: Phys. Rev. C, accepte

Heterozygous mis-sense mutations in Prkcb as a critical determinant of anti-polysaccharide antibody formation

To identify rate-limiting steps in T cell-independent type 2 (TI-2) antibody production against polysaccharide antigens, we performed a genome-wide screen by immunizing several hundred pedigrees of C57BL/6 mice segregating ENU-induced mis-sense mutations. Two independent mutations, Tilcara and Untied, were isolated that semi-dominantly diminished antibody against polysaccharide but not protein antigens. Both mutations resulted from single amino acid substitutions within the kinase domain of Protein Kinase C Beta (PKCβ). In Tilcara, a Ser552>Pro mutation occurred in helix G, in close proximity to a docking site for the inhibitory N-terminal pseudosubstrate domain of the enzyme, resulting in almost complete loss of active, autophosphorylated PKCβI whereas the amount of alternatively spliced PKCβII protein was not markedly reduced. Circulating B cell subsets were normal and acute responses to BCR-stimulation such as CD25 induction and initiation of DNA synthesis were only measurably diminished in Tilcara homozygotes, whereas the fraction of cells that had divided multiple times was decreased to an intermediate degree in heterozygotes. These results, coupled with evidence of numerous mis-sense PRKCB mutations in the human genome, identify Prkcb as a genetically sensitive step likely to contribute substantially to population variability in anti-polysaccharide antibody levels

Apparent Superluminal Behavior

The apparent superluminal propagation of electromagnetic signals seen in recent experiments is shown to be the result of simple and robust properties of relativistic field equations. Although the wave front of a signal passing through a classically forbidden region can never move faster than light, an attenuated replica of the signal is reproduced ``instantaneously'' on the other side of the barrier. The reconstructed signal, causally connected to the forerunner rather than the bulk of the input signal, appears to move through the barrier faster than light.Comment: 8 pages, no figure