3,340 research outputs found
Tidally Triggered Star Formation in Close Pairs of Galaxies: Major and Minor Interactions
We study star formation in a sample of 345 galaxies in 167 pairs and compact
groups drawn from the original CfA2 Redshift Survey and from a follow-up search
for companions. We construct our sample with attention to including pairs with
luminosity contrast |\Delta m_R| >= 2. These 57 galaxies with |\Delta m_R| >= 2
provide a set of nearby representative cases of minor interactions, a central
feature of the hierarchical galaxy formation model. Here we report the
redshifts and positions of the 345 galaxies in our sample, and of 136 galaxies
in apparent pairs that are superpositions. In the pairs sample as a whole,
there are strong correlations between the equivalent width of the H\alpha
emission line and the projected spatial and the line-of-sight velocity
separation of the pair. For pairs of small luminosity contrast, |\Delta m_R| <
2, the member galaxies show a correlation between the equivalent width of
H\alpha and the projected spatial separation of the pair. However, for pairs
with large luminosity contrast, |\Delta m_R| >= 2, we detect no correlation
between the equivalent width of H\alpha and the projected spatial separation.
The relative luminosity of the companion galaxy is more important in a
gravitational tidal interaction than the intrinsic luminosity of the galaxy.
Central star formation across the entire pairs sample depends strongly on the
luminosity ratio, |\Delta m_R|, a reasonable proxy for the mass ratio of the
pair; pairs composed of similarly luminous galaxies produce the strongest
bursts of star formation. Pairs with |\Delta m_R| >= 2 rarely have EW(H\alpha)
>~ 70 Ang.Comment: Minor revisions following journal proof
Bacillus subtilis Cw1Q (previous YjbJ) is a bifunctional enzyme exhibiting muramidase and soluble-lytic transglycosylase activities
CwIQ (previous YjbJ) is one of the putative cell wall hydrolases in Bacillus subtilis. Its domain has an amino acid sequence similar to the soluble-lytic transglycosylase (SLT) of Escherichia coli Slt70 and also goose lysozyme (muramidase). To characterize the enzyme, the domain of CwIQ was cloned and expressed in E. coil. The purified CwIQ protein exhibited cell wall hydrolytic activity. Surprisingly, RP-HPLC, mass spectrometry (MS), and MS/MS analyses showed that CwIQ produces two products, 1,6-anhydro-N-acetylmuramic acid and N-acetylmuramic acid, thus indicating that CwIQ is a bifunctional enzyme. The site-directed mutagenesis revealed that glutamic acid 85 (Glu-85) is an amino acid residue essential to both activities. (C) 2010 Elsevier Inc. All rights reserved.ArticleBIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS. 398(3):606-612 (2010)journal articl
Identification and Characterization of a Novel Polysaccharide Deacetylase C (PdaC) from Bacillus subtilis
Cell wall metabolism and cell wall modification are very important processes that bacteria use to adjust to various environmental conditions. One of the main modifications is deacetylation of peptidoglycan. The polysaccharide deacetylase homologue, Bacillus subtilis YjeA (renamed PdaC), was characterized and found to be a unique deacetylase. The pdaC deletion mutant was sensitive to lysozyme treatment, indicating that PdaC acts as a deacetylase. The purified recombinant and truncated PdaC from Escherichia coli deacetylated B. subtilis peptidoglycan and its polymer, (-GlcNAc-MurNAc[-L-Ala-D-Glu]-)(n). Surprisingly, RP-HPLC and ESI-MS/MS analyses showed that the enzyme deacetylates N-acetylmuramic acid (MurNAc) not GlcNAc from the polymer. Contrary to Streptococcus pneumoniae PgdA, which shows high amino acid sequence similarity with PdaC and is a zinc-dependent GlcNAc deacetylase toward peptidoglycan, there was less dependence on zinc ion for deacetylation of peptidoglycan by PdaC than other metal ions (Mn2+, Mg2+, Ca2+). The kinetic values of the activity toward B. subtilis peptidoglycan were K-m = 4.8 mM and k(cat) = 0.32 s(-1). PdaC also deacetylated N-acetylglucosamine (GlcNAc) oligomers with a K-m = 12.3 mM and k(cat) = 0.24 s(-1) toward GlcNAc(4). Therefore, PdaC has GlcNAc deacetylase activity toward GlcNAc oligomers and MurNAc deacetylase activity toward B. subtilis peptidoglycan.ArticleJOURNAL OF BIOLOGICAL CHEMISTRY. 287(13):9765-9776 (2012)journal articl
Penyuluhan Dan Pelatihan Keselamatan, Kesehatan, Kerja (K3) Serta Latihan Gerak Aktif Sebagai Upaya Preventif Herniated Nucleus Pulposus Dalam Meningkatkan Produktivitas Kerja Petani di Desa Susut Kabupaten Bangli
The main problem faced by partners is the lack of understanding related to occupational health and safety when carrying out work in agriculture. The possibility of accidents while working to manage rice fields often occurs and farmers do not fully understand the standards of occupational health and safety so the purpose of this service activity is to improve farmers' understanding of occupational health and safety standards as a preventive effort to prevent herniated nucleus pulposus in increasing farmers' work productivity. This activity was carried out in Susut Village, Bangli Regency using counseling and training methods involving 21 farmers. The stage of implementation of activities is divided into four parts, namely; planning stage, implementation stage, monitoring stage and evaluation stage. Evaluation is carried out by providing a questionnaire and looking at the values before and after the activity. Based on the results of the analysis of activities showed the results that; 1) there was an increase in knowledge related to occupational safety and health by 61.91%, 2) there was an increase in the understanding and implementation of active motion as a preventive effort to prevent herniated nucleus pulposus by 90.69%, (3) the work productivity of farmers was known to increase in farm yields by 25.50% after the farmers apply the principles of occupational health and safety (K3). The partner's response to this service activity is very positive and it is hoped that this will continue on an ongoing basis
Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies
We use HST NICMOS continuum and Pa-alpha observations to study the
near-infrared and star-formation properties of a representative sample of 30
local (d ~ 35-75Mpc) luminous infrared galaxies (LIRGs, infrared 8-1000um
luminosities of L_IR=11-11.9[Lsun]). The data provide spatial resolutions of
25-50pc and cover the central ~3.3-7.1kpc regions of these galaxies. About half
of the LIRGs show compact (~1-2kpc) Pa-alpha emission with a high surface
brightness in the form of nuclear emission, rings, and mini-spirals. The rest
of the sample show Pa-alpha emission along the disk and the spiral arms
extending over scales of 3-7kpc and larger. About half of the sample contains
HII regions with H-alpha luminosities significantly higher than those observed
in normal galaxies. There is a linear empirical relationship between the mid-IR
24um and hydrogen recombination (extinction-corrected Pa-alpha) luminosity for
these LIRGs, and the HII regions in the central part of M51. This relation
holds over more than four decades in luminosity suggesting that the mid-IR
emission is a good tracer of the star formation rate (SFR). Analogous to the
widely used relation between the SFR and total IR luminosity of Kennicutt
(1998), we derive an empirical calibration of the SFR in terms of the
monochromatic 24um luminosity that can be used for luminous, dusty galaxies.Comment: Accepted for publication in ApJ. Contact first author for high
qualitity version of figure
The Merging System Am 2049-691
Spectroscopic and photometric observations of the peculiar object AM 2049-691
are presented here. Its systemic velocity is V(GSR) = (10956 +-30) km/s, and
the derived distance (H(0) = 75 km/s/Mpc) results 146 Mpc. A bridge is observed
between two very distinct nuclei whose separation is about 10 kpc, as well as
two tails that emerge from the extremes SW and NE of the main body and extend
up to 41 and 58 kpc respectively. The spectral characteristics of the all
observed zones are typical of H II regions of low excitation. The internal
reddening is quit high, particularly in the NE nucleus. All the derived
equivalent widths of the H(alpha)+[N II] lines indicate enhanced star formation
compared with isolated galaxies, specially in the NE nucleus; the equivalent
width corresponding to the integrated spectrum reflects starburst activity in
the whole object, and is compatible with a merger of two disk galaxies. All the
observed characteristics of AM 2049-691 indicate it is a merger, where a
overabundance of nitrogen is detected in one of the nuclei, which has the most
evolved population and would be the most massive one. The detected total IR
emission is not very high. The integrated total color B - V corresponds to a
Sc-Scd galaxy and its average integrated population is about F7 type.
Indicative B - V colors of the nuclei, corrected for internal absorption, are
in agreement with the spectroscopic results. The central radial velocity
dispersions at the nuclei suggest that the most massive galaxy would be the
progenitor of the SW component. The observed radial velocity curve shows the
presence of two subsystems, each one associated with a different nucleus.Comment: 5 pages, 4 figure
Subaru Deep Survey V. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Photometric Properties
(abridged) We investigate photometric properties of Lyman Break Galaxies
(LBGs) at z=3.5-5.2 based on large samples of 2,600 LBGs detected in deep
(i'~27) and wide-field (1,200 arcmin^2) images taken in the Subaru Deep Field
(SDF) and the Subaru/XMM Deep Field (SXDF). The selection criteria for the LBG
samples are examined with 85 spectroscopically identified objects and by Monte
Carlo simulations. We find in the luminosity functions of LBGs (i) that the
number density of bright galaxies (M_{1700}<-22; corresponding to
SFR_{corr}>100 Msolar yr^{-1}) decreases significantly from z=4 to 5 and (ii)
that the faint-end slope of the luminosity function may become steeper towards
higher redshifts. We estimate dust extinction of z=4 LBGs with M<M^* from UV
slopes, and obtain E(B-V)=0.15+/-0.03 as the mean value. The dust extinction
remains constant with apparent luminosity, but increases with intrinsic
luminosity. We find no evolution in dust extinction between LBGs at z=3 and 4.
We investigate the evolution of UV-luminosity density at 1700A, rho, and find
that rho does not significantly change from z=3 to z=5, i.e.,
rho(z=4)/rho(z=3)=1.0+/-0.2 and rho(z=5)/rho(z=3)=0.8+/-0.4, thus the cosmic
star-formation rate (SFR) density remains constant. We find that the stellar
mass density estimated from the cosmic SFR is consistent with those derived
directly from the stellar mass function at z=0-1, but exceeds those at z~3 by a
factor of 3. We find that the ratio of the UV-luminosity density of Ly-a
emitters (LAEs) to that of LBGs is ~60% at z=5, and thus about a half of the
star formation at z=5 probably occurs in LAEs. We obtain a constraint on the
escape fraction of UV-ionizing photons produced by LBGs, f_{esc}>~0.13.Comment: 41 pages, 22 figures, ApJ in press. Paper with high resolution
figures is available at
http://hikari.astron.s.u-tokyo.ac.jp/~ouchi/work/astroph/SDS_V_VI/SDS_V.pdf
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