Fingering behavior of flame spread over solid combustibles

In this study, the fingering pattern formation and the following flamelet spreading over three different kinds of thick combustibles, i.e., Poly methacrylate (PMMA), Poly ethylene (PE) and Poly carbonate (PC) were observed and the effective Lewis number correlation was validated. Experiments were performed with a narrow channel apparatus. In addition to the kinds of solid fuel materials, the channel height and the oxidizer velocity were varied as experimental parameters. An image analysis method was developed to quantify the number, diameter and spread rate of the flamelets. Replacing the fuel thickness into the thermal thickness, the effective Lewis number which is proposed for the smoldering combustion of thin fuel is remedied to include heat transfer perpendicular to the fuel surface. The result validates that the appearance condition of the fingering instability for thick combustibles is determined by the effective Lewis number. Hence, it is concluded that the observed phenomenon is inherently similar to that of smoldering. Further, it is shown that the non-dimensional flame diameter becomes nearly constant when the fingering instability occurs. It is believed that the correlation is useful when one wants to reproduce this phenomenon in a larger scale experiment

A NuSTAR and XMM-Newton Study of the Two Most Actively Star-forming Green Pea Galaxies (SDSS J0749+3337 and SDSS J0822+2241)

We explore X-ray evidence for the presence of active galactic nuclei (AGNs) in the two most actively star-forming Green Pea galaxies (GPs), SDSS J0749+3337 and SDSS J0822+2241, which have star-formation rates (SFRs) of $123~M_\odot$ yr$^{-1}$ and $78~M_\odot$ yr$^{-1}$, respectively. The GPs have red mid-infrared (MIR) spectral energy distributions and higher 22 $\mu$m luminosities than expected from a proxy of the SFR (H$\alpha$ luminosity), consistent with hosting AGNs with 2-10 keV luminosities of $\sim10^{44}$ erg s$^{-1}$. We thus obtain and analyze the first hard ($>$ 10 keV) X-ray data observed with NuSTAR and archival XMM-Newton data below 10 keV. From the NuSTAR $\approx$20 ksec data, however, we find no significant hard X-ray emission. By contrast, soft X-ray emission with 0.5--8 keV luminosities of $\approx10^{42}$ erg s$^{-1}$ is significantly detected in both targets, which can be explained only by star formation (SF). A possible reason for the lack of clear evidence is that a putative AGN torus absorbs most of the X-ray emission. Applying a smooth-density AGN torus model, we determine minimum hydrogen column densities along the equatorial plane ($N_{\rm H}^{\rm eq}$) consistent with the non-detection. The results indicate $N_{\rm H}^{\rm eq} \gtrsim 2\times10^{24}$ cm$^{-2}$ for SDSS J0749+3337 and $N_{\rm H}^{\rm eq} \gtrsim 5\times10^{24}$ cm$^{-2}$ for SDSS J0822+2241. Therefore, the GPs may host such heavily obscured AGNs. Otherwise, no AGN exists and the MIR emission is ascribed to SF. Active SF in low-mass galaxies is indeed suggested to reproduce red MIR colors. This would imply that diagnostics based on MIR photometry data alone may misidentify such galaxies as AGNs.Comment: 12 pages, 3 tables, 5 figures, accepted for publication in Ap

L-Fucose-containing arabinogalactan-protein in radish leaves.

The carbohydrate moieties of arabinogalactan-proteins (AGPs) have β-(1 → 3)-galactan backbones to which side chains of (1 → 6)-linked β-Gal residues are attached through O-6. Some of these side chains are further substituted with other sugars. We investigated the structure of L-Fuc-containing oligosaccharides released from the carbohydrate moieties of a radish leaf AGP by digestion with α-L-arabinofuranosidase, followed by exo-β-(1 → 3)-galactanase. We detected a series of neutral β-(1 → 6)-galactooligosaccharides branching variously at O-3 of the Gal residues, together with corresponding acidic derivatives terminating in 4-O-methyl-GlcA (4-Me-GlcA) or GlcA at the non-reducing terminals. In neutral oligosaccharides with degree of polymerization (dp) mainly higher than 10, L-Fuc groups were attached through L-Ara residues as the sequence, α-L-Fucp-(1 → 2)-α-L-Araf-(1 →. This sequence was verified by isolation of the pentasaccharide α-L-Fuc-(1 → 2)-α-L-Araf-(1 → 3)-β-Gal-(1 → 6)-β-Gal-(1 → 6)-Gal upon digestion of the higher oligosaccharides with endo-β-(1 → 6)-galactanase. By contrast, in lower polymerized (predominantly dp 4) acidic oligosaccharides, L-Fuc groups were attached directly at the non-reducing terminals through α-(1 → 2)-linkages, resulting in the release of the tetrasaccharides, α-L-Fucp-(1 → 2)-β-GlcA-(1 → 6)-β-Gal-(1 → 6)-Gal and α-L-Fucp-(1 → 2)-β-4-Me-GlcA-(1 → 6)-β-Gal-(1 → 6)-Gal. In long acidic oligosaccharides with dp mainly higher than 13, L-Fuc groups localized on branches were attached to the uronic acids directly and/or L-Ara residues as in the neutral oligosaccharides.The authors would like to thank Prof. M. Hisamatsu, Mie University, Tsu, Japan, for a gift of cyclic β-(1→2)-glucan. This work was supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (Grant-in-Aid for Scientific Research no. 23570048 to Y.T. and no. 24114006 to Y.T. and T.K.). Support was also provided by BBSRC Sustainable Bioenergy Centre: Cell wall sugars program (Grant No. BB/G016240/1) to P.D.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.carres.2015.07.00

Water Soluble Aluminum Paste Using Polyvinyl Alcohol for Silicon Solar Cells

Screen-printing aluminum is still dominantly used in the solar cell fabrication process. Ethyl cellulose is one of the main contents of screen-printing pastes that require dichloromethane for its cleaning process, a substance renowned for being extremely toxic and threatening to the human body. Developing environmental friendly aluminum pastes is essential in order to provide an alternative to the commercial pastes. In this work, new, nontoxic polyvinyl alcohol-based aluminum pastes are introduced. Polyvinyl alcohol was used as a soluble polymer that can be synthesized without saponification and that is also soluble in water. Three different pastes were developed using different recipes including many aluminum particle sizes varying from 3.0 to 45 μm, aluminum oxide with particle sizes between 35 and 50 μm, and acetic acid. Evaluation of the pastes was carried out by Scanning Electron Microscope (SEM) image analysis, sheet resistance measurements, and fabricating silicon solar cells using each paste. Solar cells with 15.6% efficiency were fabricated by nonvacuum processing on CZ-Si p-type wafers using developed aluminum pastes on the back side

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) VIII. A less biased view of the early co-evolution of black holes and host galaxies

We present ALMA [CII] line and far-infrared (FIR) continuum observations of three $z > 6$ low-luminosity quasars ($M_{\rm 1450} > -25$) discovered by our Subaru Hyper Suprime-Cam (HSC) survey. The [CII] line was detected in all three targets with luminosities of $(2.4 - 9.5) \times 10^8~L_\odot$, about one order of magnitude smaller than optically luminous ($M_{\rm 1450} \lesssim -25$) quasars. The FIR continuum luminosities range from $< 9 \times 10^{10}~L_\odot$ (3$\sigma$ limit) to $\sim 2 \times 10^{12}~L_\odot$, indicating a wide range in star formation rates in these galaxies. Most of the HSC quasars studied thus far show [CII]/FIR luminosity ratios similar to local star-forming galaxies. Using the [CII]-based dynamical mass ($M_{\rm dyn}$) as a surrogate for bulge stellar mass ($M_{\rm bulge}$), we find that a significant fraction of low-luminosity quasars are located on or even below the local $M_{\rm BH} - M_{\rm bulge}$ relation, particularly at the massive end of the galaxy mass distribution. In contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. Given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. Almost all of the quasars presented in this work are growing their black hole mass at much higher pace at $z \sim 6$ than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local $M_{\rm BH} - M_{\rm bulge}$ relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at $z \sim 6$, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.Comment: 19 pages, 11 figures, 4 tables. Accepted for publication in Publications of the Astronomical Society of Japan (PASJ

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) III. Star formation properties of the host galaxies at z≳6z \gtrsim 6 studied with ALMA

We present our ALMA Cycle 4 measurements of the [CII] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity ($M_{\rm 1450} > -25$) quasars at $z \gtrsim 6$ discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [CII] line and FIR continuum luminosities lie in the ranges $L_{\rm [CII]} = (3.8-10.2) \times 10^8~L_\odot$ and $L_{\rm FIR} = (1.2-2.0) \times 10^{11}~L_\odot$, which are at least one order of magnitude smaller than those of optically-luminous quasars at $z \gtrsim 6$. We estimate the star formation rates (SFR) of our targets as $\simeq 23-40~M_\odot ~{\rm yr}^{-1}$. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The $L_{\rm [CII]}/L_{\rm FIR}$ ratios of the hosts, $\simeq (2.2-8.7) \times 10^{-3}$, are fully consistent with local star-forming galaxies. Using the [CII] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as $\simeq (1.4-8.2) \times 10^{10}~M_\odot$. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at $z \sim 6$, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of the most of low-luminosity quasars including the HSC ones are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole-host galaxy evolution.Comment: 20 pages, 9 figures, 4 tables. Accepted for publication in PAS

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XIV. A Candidate Type-II Quasar at z=6.1292

We present deep Keck/MOSFIRE near-infrared spectroscopy of a strong Lyman alpha emitting source at z=6.1292, HSC J142331.71-001809.1, which was discovered by the SHELLQS program from imaging data of the Subaru Hyper Suprime-Cam (HSC) survey. This source is one of five objects that show unresolved (10^44 erg s-1) Lyman alpha emission lines at absolute 1450 angstrom continuum magnitudes of M1450~-22 mag. Its rest-frame Lyman alpha equivalent width (EW) is 370+/-30 angstrom. In the 2 hour Keck/MOSFIRE spectrum in Y band, the high-ionization CIV 1548,1550 doublet emission line was clearly detected with FWHM =120+/-20 km s-1 and a total rest-frame EW of 37-5+6 angstrom. We also report the detection of weak continuum emission, and the tentative detection of OIII] 1661,1666 in the 4 hour J band spectrum. Judging from the UV magnitude, line widths, luminosities, and EWs of Lyman alpha and CIV, we suggest that this source is a reionization-era analog of classical type-II AGNs, although there is a possibility that it represents a new population of AGN/galaxy composite objects in the early universe. We compare the properties of J1423-0018 to intermediate-redshift type-II AGNs and CIV emitters seen in z=6-7 galaxy samples. Further observations of other metal emission lines in the rest-frame UV or optical, and X-ray follow-up observations of the z=6-7 narrow-line quasars are needed for more robust diagnostics and to determine their nature.Comment: 15 pages, 8 figures, accepted for publication in the Astrophysical Journa

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IX. Identification of Two Red Quasars at z > 5.6

We present the first discovery of dust-reddened quasars (red quasars) in the high-z universe (z >5.6). This is a result from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which is based on the sensitive multi-band optical imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We identified four red quasar candidates from the spectroscopically confirmed 93 high-z quasars in the SHELLQs sample, based on detections in the Wide-field Infrared Survey Explorer (WISE) data at 3.4 and 4.6 um (rest-frame ~5000-6500 A). The amount of dust reddening was estimated with spectral energy distribution (SED) fits over optical and mid-infrared wavelengths. Two of the four candidates were found to be red quasars with dust reddening of E(B-V) > 0.1. The remaining SHELLQs quasars without individual WISE detections are significantly fainter in the WISE bands and bluer than the red quasars, although we did detect them in the W1 band in a stacked image. We also conducted the same SED fits for high-z optically-luminous quasars, but no red quasar was found. This demonstrates the power of Subaru HSC to discover high-z red quasars, which are fainter than the limiting magnitudes of past surveys in the rest-frame ultraviolet, due to dust extinction.Comment: Accepted for publication in PAS

Discovery of the First Low-Luminosity Quasar at z > 7

We report the discovery of a quasar at z = 7.07, which was selected from the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. This quasar, HSC J124353.93+010038.5, has an order of magnitude lower luminosity than do the other known quasars at z > 7. The rest-frame ultraviolet absolute magnitude is M1450 = -24.13 +/- 0.08 mag and the bolometric luminosity is Lbol = (1.4 +/- 0.1) x 10^{46} erg/s. Its spectrum in the optical to near-infrared shows strong emission lines, and shows evidence for a fast gas outflow, as the C IV line is blueshifted and there is indication of broad absorption lines. The Mg II-based black hole mass is Mbh = (3.3 +/- 2.0) x 10^8 Msun, thus indicating a moderate mass accretion rate with an Eddington ratio 0.34 +/- 0.20. It is the first z > 7 quasar with sub-Eddington accretion, besides being the third most distant quasar, known to date. The luminosity and black hole mass are comparable to, or even lower than, those measured for the majority of low-z quasars discovered by the Sloan Digital Sky Survey, and thus this quasar likely represents a z > 7 counterpart to quasars commonly observed in the low-z universe.Comment: Accepted for publication in ApJ Letter