Bayesian optimization for computationally extensive probability distributions

An efficient method for finding a better maximizer of computationally extensive probability distributions is proposed on the basis of a Bayesian optimization technique. A key idea of the proposed method is to use extreme values of acquisition functions by Gaussian processes for the next training phase, which should be located near a local maximum or a global maximum of the probability distribution. Our Bayesian optimization technique is applied to the posterior distribution in the effective physical model estimation, which is a computationally extensive probability distribution. Even when the number of sampling points on the posterior distributions is fixed to be small, the Bayesian optimization provides a better maximizer of the posterior distributions in comparison to those by the random search method, the steepest descent method, or the Monte Carlo method. Furthermore, the Bayesian optimization improves the results efficiently by combining the steepest descent method and thus it is a powerful tool to search for a better maximizer of computationally extensive probability distributions.Comment: 13 pages, 5 figure

Sequential Formation of Low-Mass Stars in the BRC 14 Region

We have carried out a deep near-infrared survey of a bright-rimmed molecular cloud, BRC 14 (IC 1848A). The 10 sigma limiting magnitude of the survey is 17.7 mag at the K-band. Seventy-four sources are classified as young stellar object (YSO) candidates based on the near-infrared color-color diagram. The faintest YSO candidates may have masses of an order of tenths of the solar mass, assuming the age of 1 Myr. We examined three values as indicators of star formation; fraction of the YSO candidates, extinctions of all sources, and near-infrared excesses of the YSO candidates. All indicators increase from outside of the rim to the center of the molecular cloud, which suggests that the formation of the low-mass stars in the BRC 14 region proceeds from outside to the center of the cloud.Comment: 12 pages, 5 figures, 1 table, PASJ accepte

Identification of Ornithine-lactam Converted from Arginine in Streptomyces incarnatus NRRL8089

Sinefungin is a nucleoside antibiotic, in which a molecule of L-ornithine is linked to the 5' end of adenosine through a C-C bond. The antibiotic was isolated from the culture broth of Streptomyces incarnatus. For the purpose of detecting intermediate of sinefungin biosynthesis, resting cell suspensions were incubated with supplemental L-arginine, and L-ornithine. 50mM Arginine was converted to a compound X that has low polarity. 50mM ornithine was not converted and remained in reaction solution. Compound X was purified using HPLC, and analyzed using (1)H-NMR and FAB-MS. These analyses showed that a compound X is "ornithine-lactam" (Mw＝114), which has a structure of circularized ornithine. These results indicated that S. incarnatus has an enzyme that converts arginine to ornithine-lactam. Such an enzyme has never been reported, and suggested that it may be relevant to sinefungin biosynthesis.シネフンギンは抗真菌，抗マラリア活性を有する核酸系抗生物質であり，放線菌 S. incarnatus により生合成される．シネフンギンはアデノシンとオルニチンがＣﾝＣ結合した構造であり，無細胞抽出液での取り込み実験からＬﾝアルギニンと ATP から生合成されると推測される．Ｌﾝアルギニン，Ｌﾝオルニチンを S. incarnatus の休止菌体反応系への投与を行いシネフンギン中間体の探索を行った．その結果50ﾋアルギニンは24時間以内に低極性化合物へと変換された．一方50ﾋオルニチンは変換されず反応液中に残存した．HPLC で化合物を精製し，1HﾝNMR，FABﾝMS での分析の結果オルニチン環状モノペプチド，「オルニチンラクタム」（分子量114）であることを明らかにした．この結果は S. incarnatus がアルギニンからオルニチンラクタムへの変換酵素を有する事を示唆する．このような酵素の報告例はこれまでになく，ニ次代謝酵素であることが示唆され，シネフンギン生合成との関連性に興味が持たれる

Mapping dust column density in dark clouds by using NIR scattered light : Case of the Lupus 3 dark cloud

We present a method of mapping dust column density in dark clouds by using near-infrared scattered light. Our observations of the Lupus 3 dark cloud indicate that there is a well defined relation between (1) the H-Ks color of an individual star behind the cloud, i.e., dust column density, and (2) the surface brightness of scattered light toward the star in each of the J, H, and Ks bands. In the relation, the surface brightnesses increase at low H-Ks colors, then saturate and decrease with increasing H-Ks. Using a simple one-dimensional radiation transfer model, we derive empirical equations which plausibly represent the observed relationship between the surface brightness and the dust column density. By using the empirical equations, we estimate dust column density of the cloud for any directions toward which even no background stars are seen. We obtain a dust column density map with a pixel scale of 2.3 x 2.3 arcsec^2 and a large dynamic range up to Av = 50 mag. Compared to the previous studies by Juvela et al., this study is the first to use color excess of the background stars for calibration of the empirical relationship and to apply the empirical relationship beyond the point where surface brightness starts to decrease with increasing column density

FGF-10 Stimulates Limb Regeneration Ability in Xenopus laevis

AbstractBy reciprocal transplantation experiments with regenerative and nonregenerative Xenopus limbs, we recently demonstrated that the regenerative capacity of a Xenopus limb depends on mesenchymal tissue and we suggested that fgf-10 is likely to be involved in this capacity (Yokoyama et al., 2000, Dev. Biol. 219, 18–29). However, the data obtained in that study are not conclusive evidence that FGF-10 is responsible for the regenerative capacity. We therefore investigated the role of FGF-10 in regenerative capacity by directly introducing FGF-10 protein into nonregenerative Xenopus limb stumps. Exogenously applied FGF-10 successfully stimulated the regenerative capacity, resulting in the reinduction of all gene expressions (including shh, msx-1, and fgf-10) that we examined and the regeneration of well-patterned limb structures. We report here for the first time that a certain molecule activates the regenerative capacity of Xenopus limb, and this finding suggests that FGF-10 could be a key molecule in possible regeneration of nonregenerative limbs in higher vertebrates

Boltzmann sampling with quantum annealers via fast Stein correction

Despite the attempts to apply a quantum annealer to Boltzmann sampling, it is still impossible to perform accurate sampling at arbitrary temperatures. Conventional distribution correction methods such as importance sampling and resampling cannot be applied, because the analytical expression of sampling distribution is unknown for a quantum annealer. Stein correction (Liu and Lee, 2017) can correct the samples by weighting without the knowledge of the sampling distribution, but the naive implementation requires the solution of a large-scale quadratic program, hampering usage in practical problems. In this letter, a fast and approximate method based on random feature map and exponentiated gradient updates is developed to compute the sample weights, and used to correct the samples generated by D-Wave quantum annealers. In benchmarking problems, it is observed that the residual error of thermal average calculations is reduced significantly. If combined with our method, quantum annealers may emerge as a viable alternative to long-established Markov chain Monte Carlo methods.Comment: 5 pages, 2 figure

Near-Infrared Extinction in The Coalsack Globule 2

We have conducted J, H, and Ks imaging observations for the Coalsack Globule 2 with the SIRIUS infrared camera on the IRSF 1.4 m telescope at SAAO, and determined the color excess ratio, E(J-H)/E(H-Ks). The ratio is determined in the same photometric system as our previous study for the rho Oph and Cha clouds without any color transformation; this enables us to directly compare the near-infrared extinction laws among these regions. The current ratio E(J-H)/E(H-Ks) = 1.91 +- 0.01 for the extinction range 0.5 < E(J-H) <1.8 is significantly larger than the ratios for the rho Oph and Cha clouds (E(J-H)/E(H-Ks) = 1.60-1.69). This ratio corresponds to a large negative index alpha = 2.34 +- 0.01 when the wavelength dependence of extinction is approximated by a power law which might indicate little growth of dust grains, or larger abundance of dielectric non-absorbing components such as silicates, or both in this cloud. We also confirm that the color excess ratio for the Coalsack Globule 2 has a trend of increasing with decreasing optical depth, which is the same trend as the rho Oph and Cha clouds have.Comment: 13 pages, 5 figures, and 2 tables, Ap

FGF7 and FGF10 Directly Induce the Apical Ectodermal Ridge in Chick Embryos

AbstractDuring vertebrate limb development, the apical ectodermal ridge (AER) plays a vital role in both limb initiation and distal outgrowth of the limb bud. In the early chick embryo the prelimb bud mesoderm induces the AER in the overlying ectoderm. However, the direct inducer of the AER remains unknown. Here we report that FGF7 and FGF10, members of the fibroblast growth factor family, are the best candidates for the direct inducer of the AER. FGF7 induces an ectopic AER in the flank ectoderm of the chick embryo in a different manner from FGF1, -2, and -4 and activates the expression of Fgf8, an AER marker gene, in a cultured flank ectoderm without the mesoderm. Remarkably, FGF7 and FGF10 applied in the back induced an ectopic AER in the dorsal median ectoderm. Our results suggest that FGF7 and FGF10 directly induce the AER in the ectoderm both of the flank and of the dorsal midline and that these two regions have the competence for AER induction. Formation of the AER of the dorsal median ectoderm in the chick embryo is likely to appear as a vestige of the dorsal fin of the ancestors

Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands

We have determined the ratios of total to selective extinction directly from observations in the optical V band and near-infrared J band toward the Galactic center. The OGLE (Optical Gravitational Lensing Experiment) Galactic bulge fields have been observed with the SIRIUS camera on the IRSF telescope, and we obtain A(V)/E(V-J)=1.251+-0.014 and A(J)/E(V-J)=0.225+-0.007. From these ratios, we have derived A(J)/A(V) = 0.188+-0.005; if we combine A(J)/A(V) with the near-infrared extinction ratios obtained by Nishiyama et al. for more reddened fields near the Galactic center, we get A(V) : A(J) : A(H) : A(Ks) = 1 : 0.188 : 0.108 : 0.062, which implies steeply declining extinction toward the longer wavelengths. In particular, it is striking that the Ks band extinction is \approx 1/16 of the visual extinction A(V) much smaller than one tenth of A(V) so far employed.Comment: 8 pages, 7 figures, Accepted for publication in Ap