61 research outputs found
Bigradient Phase Referencing
We propose bigradient phase referencing (BPR), a new radio-observation
technique, and report its performance using the Japanese
very-long-baseline-interferometry network (JVN). In this method, a weak source
is detected by phase-referencing using a primary calibrator, in order to play a
role as a secondary calibrator for phase-referencing to a weak target. We will
be given the opportunity to select a calibrator from lots of milli-Jansky
sources, one of which may be located at the position closer to the target. With
such a smaller separation, high-quality phase-referencing can be achieved.
Furthermore, a subsequent more-sophisticated calibration can relocate array's
focus to a hypothetical point much closer to the target; a higher quality of
phase referencing is available. Our demonstrative observations with strong
radio sources have proved the capabilities of BPR in terms of image dynamic
ranges and astrometric reproducibility. The image dynamic range on a target has
been improved with a factor of about six compared to that of normal
phase-referencing; the resultant position difference of target's emission
between two epochs was only 62+-50 micro-arcsecond, even with less than 2300-km
baselines at 8.4 GHz and fast-switching of a target-calibrator pair of a
2.1-degree separation.Comment: 10 pages, 4 figures, accepted for publication in PAS
Japanese VLBI Network observations of radio-loud narrow-line Seyfert 1 galaxies
We performed phase-reference very long baseline interferometry (VLBI)
observations on five radio-loud narrow-line Seyfert 1 galaxies (NLS1s) at 8.4
GHz with the Japanese VLBI Network (JVN). Each of the five targets (RXS
J08066+7248, RXS J16290+4007, RXS J16333+4718, RXS J16446+2619, and B3
1702+457) in milli-Jansky levels were detected and unresolved in
milli-arcsecond resolutions, i.e., with brightness temperatures higher than
10^7 K. The nonthermal processes of active galactic nuclei (AGN) activity,
rather than starbursts, are predominantly responsible for the radio emissions
from these NLS1s. Out of the nine known radio-loud NLS1s, including the ones
chosen for this study, we found that the four most radio-loud objects
exclusively have inverted spectra. This suggests a possibility that these NLS1s
are radio-loud due to Doppler beaming, which can apparently enhance both the
radio power and the spectral frequency.Comment: 8 pages, 2 figures, accepted for publication in PAS
Characterization of Novel Carbazole Catabolism Genes from Gram-Positive Carbazole Degrader Nocardioides aromaticivorans IC177
Nocardioides aromaticivorans IC177 is a gram-positive carbazole degrader. The genes encoding carbazole degradation (car genes) were cloned into a cosmid clone and sequenced partially to reveal 19 open reading frames. The car genes were clustered into the carAaCBaBbAcAd and carDFE gene clusters, encoding the enzymes responsible for the degradation of carbazole to anthranilate and 2-hydroxypenta-2,4-dienoate and of 2-hydroxypenta-2,4-dienoate to pyruvic acid and acetyl coenzyme A, respectively. The conserved amino acid motifs proposed to bind the Rieske-type [2Fe-2S] cluster and mononuclear iron, the Rieske-type [2Fe-2S] cluster, and flavin adenine dinucleotide were found in the deduced amino acid sequences of carAa, carAc, and carAd, respectively, which showed similarities with CarAa from Sphingomonas sp. strain KA1 (49% identity), CarAc from Pseudomonas resinovorans CA10 (31% identity), and AhdA4 from Sphingomonas sp. strain P2 (37% identity), respectively. Escherichia coli cells expressing CarAaAcAd exhibited major carbazole 1,9a-dioxygenase (CARDO) activity. These data showed that the IC177 CARDO is classified into class IIB, while gram-negative CARDOs are classified into class III or IIA, indicating that the respective CARDOs have diverse types of electron transfer components and high similarities of the terminal oxygenase. Reverse transcription-PCR (RT-PCR) experiments showed that the carAaCBaBbAcAd and carDFE gene clusters are operonic. The results of quantitative RT-PCR experiments indicated that transcription of both operons is induced by carbazole or its metabolite, whereas anthranilate is not an inducer. Biotransformation analysis showed that the IC177 CARDO exhibits significant activities for naphthalene, carbazole, and dibenzo-p-dioxin but less activity for dibenzofuran and biphenyl
Depth error correction for projector-camera based consumer depth cameras
Abstract This paper proposes a depth measurement error model for consumer depth cameras such as the Microsoft Kinect, and a corresponding calibration method. These devices were originally designed as video game interfaces, and their output depth maps usually lack sufficient accuracy for 3D measurement. Models have been proposed to reduce these depth errors, but they only consider camera-related causes. Since the depth sensors are based on projector-camera systems, we should also consider projector-related causes. Also, previous models require disparity observations, which are usually not output by such sensors, so cannot be employed in practice. We give an alternative error model for projector-camera based consumer depth cameras, based on their depth measurement algorithm, and intrinsic parameters of the camera and the projector; it does not need disparity values. We also give a corresponding new parameter estimation method which simply needs observation of a planar board. Our calibrated error model allows use of a consumer depth sensor as a 3D measuring device. Experimental results show the validity and effectiveness of the error model and calibration procedure
- …