The spectrum of gravitational waves in Randall-Sundrum braneworld cosmology

We study the generation and evolution of gravitational waves (tensor perturbations) in the context of Randall-Sundrum braneworld cosmology. We assume that the initial and final stages of the background cosmological model are given by de Sitter and Minkowski phases, respectively, and they are connected smoothly by a radiation-dominated phase. This setup allows us to discuss the quantum-mechanical generation of the perturbations and to see the final amplitude of the well-defined zero mode. Using the Wronskian formulation, we numerically compute the power spectrum of gravitational waves, and find that the effect of initial vacuum fluctuations in the Kaluza-Klein modes is subdominant, contributing not more than 10% of the total power spectrum. Thus it is confirmed that the damping due to the Kaluza-Klein mode generation and the enhancement due to the modification of the background Friedmann equation are the two dominant effects, but they cancel each other, leading to the same spectral tilt as the standard four-dimensional result. Kaluza-Klein gravitons that escape from the brane contribute to the energy density of the dark radiation at late times. We show that a tiny amount of the dark radiation is generated due to this process.Comment: 10 pages, 5 figures; v2: published versio

Icosahedral quasicrystal and 1/1 cubic approximant in Au-Al-Yb alloys

A P-type icosahedral quasicrystal is formed in Au-Al-Yb alloy of which 6-dimensional lattice parameter a6D = 7.448 {\AA}. The composition of the quasicrystal was analyzed to be Au51Al34Yb15. This quasicrystal is formed in as-cast alloys, and is regarded as metastable because of decomposition into other crystalline phases by annealing at 700 \degree C. Among Tsai-type quasicrystals, this quasicrystal is situated just between Zn-Sc group with smaller a6D and larger Cd-Yb group. Intermediate valence of Yb recently observed in this quasicrystal may be due to this unique situation, namely smaller major component Au-Al than in Cd-Yb. The predominant phase in the annealed specimen is a 1/1 cubic approximant with lattice parameter a = 14.500 {\AA} belonging to the space group Im-3 . This phase is stable at the composition Au51Al35Yb14 at 700 \degree C. Rietveld structural analysis indicated that the crystal structure is understood as periodic arrangement of Tsai-type clusters each including four Au-Al atoms at their centers. Chemical ordering of Au and Al is characteristics of this approximant.Comment: 20 pages including 1 table and 7 figure

Unidirectional control of optically induced spin waves

Unidirectional control of optically induced spin waves in a rare-earth iron garnet crystal is demonstrated. We observed the interference of two spin-wave packets with different initial phases generated by circularly polarized light pulses. This interference results in unidirectional propagation if the spin-wave sources are spaced apart at 1/4 of the wavelength of the spin waves and the initial phase difference is set to pi/2. The propagating direction of the spin wave is switched by the polarization helicity of the light pulses. Moreover, in a numerical simulation, applying more than two spin-wave sources with a suitable polarization and spot shape, arbitrary manipulation of the spin wave by the phased array method was replicated

Budget Policy and Economic Stability in Postwar Japan

The purpose of this paper is to complement existing studies of postwar Japanese growth by measuring the effects of various types of budget changes and evaluating their impact on the achievement of economic stability and balanced growth during the sixteen-year period from 1952 through 1967.Center for Research on Economic Development, University of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/100983/1/ECON425.pd

Sortase A-assisted metabolic enzyme ligation in Escherichia coli

We demonstrated the metabolic enzyme ligation by sortase A-mediated ligation (sortagging) for the redirection of metabolic flux thorough metabolic channeling. Staphylococcal sortase A (SrtA) is utilized for the ligation of metabolic enzymes. SrtA is transpeptidase, which recognizes Leu-Pro-Xaa-Thr-Gly sequences (LP tag) and cleaves between Thr and Gly, and subsequently links amino group of oligoglycine (G tag) thorough a native peptide bond. Sortagging enables to conjugate protein with other molecules in a site-specific manner. Minimal modifications of protein with short peptide tags; LP tag and G tag are only required for site-specific ligation. Hence, sortagging has been utilized for preparing a variety of bioconjugation not only in vitro but also in vivo.1 In current study, we hypothesize that SrtA-mediated metabolic enzyme ligation in cytoplasm of Escherichia coli facilitates processing metabolic intermediate, and redirects metabolic fluxes to desired pathway. As proof of concept, we constructed acetate producing E. coli with engineered endogenous metabolic pathway, which redirect central metabolic fluxes to acetate producing flux by the induction of chemical additives (Figure 1). The expression of SrtA was controlled by Lac operating promoter, metabolic channeling was videlicet occurred by the addition of IPTG. Acetyl-CoA was chosen as the intermediate model because acetyl-CoA is one of the most important central metabolic intermediates, which is converted to alcohols, fatty acids, and mevalonate derivatives. In this study, we tested covalent linking of pyruvate-formate lyase and phosphate acetyltransferase by sortase A-mediated ligation and evaluated the production of acetate. The time point of addition of IPTG was not critical for facilitating metabolic enzyme ligation, and acetate production increased upon expression of sortase A. These results show that sortase A-mediated enzyme ligation enhances an acetate-producing flux in E. coli. We have validated that sortase A-mediated enzyme ligation offers a metabolic channeling approach to redirect a central flux to a desired flux.2 Please click Additional Files below to see the full abstract