ELECTROPHORETIC AND ENZYMATIC IDENTIFICATION OF PROTEINS ASSOCIATED WITH THE DEVELOPMENT OF COMPETENCE IN BACILLUS SUBTILIS

A two-dimensional zymogram procedure for the analysis of nucleases is described. Using purified deoxyribonuclease I (bovine pancreas), as little as 10 pg of nuclease can be detected. Isoelectric focusing (IEF) and non-equilibrium pH gradient electrophoresis (NEPHGE) were compared as first dimensions, in combination with SDS electrophoresis as the second dimension, in analyzing nucleases in lysates of Bacillus subtilis. All renaturable nuclease activities detected following SDS electrophoresis alone were resolved in NEPHGE-SDS electrophoresis gels whereas, in IEF-SDS gels, most were either at the basic end or were not present in the second dimensional gel. This method of analysis has revealed a complexity in nuclease species in B. subtilis not previously recognized. Eighty-three discrete nuclease activities have been detected in B. subtilis lysates. These nucleases have been characterized with respect to monomeric molecular weights, cation-activation requirements, and preference for single or double stranded substrate. Substrate and cation analysis reveals a minimum of 16 classes of activities. The nucleases identified in this study are compared to those previously reported in B. subtilis. The total protein composition and nuclease composition of cellular lysates from competent and non-competent B. subtilis strain SB25 and several transformation-defective mutants of SB25 has been examined by two-dimensional electrophoretic and zymogram analysis. Thirty-six competence-associated polypeptides have been identified. Nuclease analysis has revealed that the development of competence is accompanied by the induction of 4 nucleases and the suppression of 6 nucleases. Three of the competence-associated nucleases (monomeric MW; 17,500, 18,000, and 18,500) are primarily activated by Mn(\u272+) and are most active on denatured DNA. The fourth (monomeric MW; 17,000) is also Mn(\u272+)-activated but is distinguished by its preference for native DNA. The nuclease activities which are reduced in competent cells are all primarily Mn(\u272+)-activated. Three of these nucleases (monomeric MW; 18,000, 21,000, and 24,000) show equal activity on native and denatured DNA. The remaining three (monomeric MW; 17,000, 18,500, and 19,250), show a preference for native DNA. Transformation-defective mutants have been identified which have a reduced level of the 17,000 MW competence-associated nuclease. These mutants are deficient in uptake and the ability to inactivate exogenous DNA. In addition to the suppression of the 17,000 MW nuclease, these mutants fail to induce a large number of additional competence-associated polypeptides

A comprehensive study of Hα\alpha emitters at z∼z \sim 0.62 in the DAWN survey: the need for deep and wide regions

We present new estimates of the luminosity function (LF) and star formation rate density (SFRD) for an H$\alpha$ selected sample at $z\sim0.62$ from the Deep And Wide Narrow-band (DAWN) survey. Our results are based on a new H$\alpha$ sample in the extended COSMOS region (compared to Coughlin et al. 2018) with the inclusion of flanking fields, resulting in a total area coverage of $\sim$1.5 deg$^2$. A total of 241 H$\alpha$ emitters were selected based on robust selection criteria using spectro-photometric redshifts and broadband color-color classification. We explore the effect of different dust correction prescriptions by calculating the LF and SFRD using a constant dust extinction correction, A{$_{\textrm{H}\alpha}=1$} mag, a luminosity-dependent correction, and a stellar-mass dependent correction. The resulting H$\alpha$ LFs are well fitted using Schechter functions with best-fit parameters: L$^*=10^{42.24}$ erg s$^{-1}$, $\phi^*=10^{-2.85}$ Mpc$^{-3}$, $\alpha = -1.62$ for constant dust correction, L$^*=10^{42.31}$ erg s$^{-1}$, $\phi^*=10^{-2.8}$ Mpc$^{-3}$, $\alpha=-1.39$ for luminosity-dependent dust correction, and L$^*=10^{42.36}$ erg s$^{-1}$, $\phi^*=10^{-2.91}$ Mpc$^{-3}$, $\alpha = -1.48$, for stellar mass-dependent dust correction. The deep and wide nature of the DAWN survey effectively samples H$\alpha$ emitters over a wide range of luminosities, thereby providing better constraints on both the faint and bright end of the LF. Also, the SFRD estimates $\rho_{\textrm{SFR}}=10^{-1.39}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (constant dust correction), $\rho_{\textrm{SFR}}=10^{-1.47}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (luminosity-dependent dust correction), and $\rho_{\textrm{SFR}}=10^{-1.49}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (stellar mass-dependent dust correction) are in good agreement with the evolution of SFRD across redshifts ($0 < z < 2$) seen from previous H$\alpha$ surveys.Comment: 16 pages, 8 figures, Accepted for publication in Ap

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M&gt;70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0&lt;e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM