High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified » E 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S XVI (  E 3.44 keV rest-frame)-a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.

This paper proposes a multichannel source separation technique called the multichannel variational autoencoder (MVAE) method, which uses a conditional VAE (CVAE) to model and estimate the power spectrograms of the sources in a mixture. By training the CVAE using the spectrograms of training examples with source-class labels, we can use the trained decoder distribution as a universal generative model capable of generating spectrograms conditioned on a specified class label. By treating the latent space variables and the class label as the unknown parameters of this generative model, we can develop a convergence-guaranteed semi-blind source separation algorithm that consists of iteratively estimating the power spectrograms of the underlying sources as well as the separation matrices. In experimental evaluations, our MVAE produced better separation performance than a baseline method.Index Terms-Blind source separation, multichannel non-negative matrix factorization, variational autoencoders (VAEs)

NAD(P)-dependent dehydrogenases differ according to their coenzyme preference: some prefer NAD, others NADP, and still others exhibit dual cofactor specificity. The structure of a newly identified archaeal homoserine dehydrogenase showed this enzyme to have a strong preference for NADP. However, NADP did not act as a cofactor with this enzyme, but as a strong inhibitor of NADdependent homoserine oxidation. Structural analysis and site-directed mutagenesis showed that the large number of interactions between the cofactor and the enzyme are responsible for the lack of reactivity of the enzyme towards NADP. This observation suggests this enzyme exhibits a new variation on cofactor binding to a dehydrogenase: very strong NADP binding that acts as an obstacle to NAD(P)-dependent dehydrogenase catalytic activity.Homoserine dehydrogenase (HseDH, EC 1.1.1.3) is a key enzyme in the biosynthetic pathway from aspartate to homoserine (Hse), which is a common precursor for the synthesis of three amino acids, methionine, threonine and isoleucine in plants and microorganisms [1][2][3] . In this pathway, aspartate is first phosphorylated to β -aspartyl phosphate (β -Ap) by aspartate kinase, after which L-aspartate-β -semialdehyde (Asa) dehydrogenase catalyzes the conversion of β -Ap to Asa. The third enzyme in the pathway, HseDH, catalyzes the NAD(P)H-dependent reduction of Asa to Hse. Subsequent metabolism of Hse yields methionine, threonine or isoleucine, which are all essential in humans. Because HseDH is central to the synthesis of these amino acids, regulation of the enzyme by its end products has been extensively studied in bacteria, yeast and plants at both the activity and genetic levels 4-7 . In particular, threonine-dependent feedback regulation to control HseDH activity has been analyzed in detail. Additionally, HseDH is thought to be a potential target for the structure-based design of antibiotics or herbicides, as the enzyme is not present in mammals 1,2,8 . However, information about the structure of HseDH remains limited. Indeed, the crystal structures of only the Saccharomyces cerevisiae and Thermus thermophilus enzymes have so far been reported 9,10 .

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Extending the earlier measurements reported in Hitomi collaboration (2016, Nature, 535, 117), we examine the atmospheric gas motions within the central 100 kpc of the Perseus cluster using observations obtained with the Hitomi satellite. After correcting for the point spread function of the telescope and using optically thin emission lines, we find that the line-of-sight velocity dispersion of the hot gas is remarkably low and mostly uniform. The velocity dispersion reaches a maxima of approximately 200 km s−1 toward the central active galactic nucleus (AGN) and toward the AGN inflated northwestern “ghost” bubble. Elsewhere within the observed region, the velocity dispersion appears constant around 100 km s−1. We also detect a velocity gradient with a 100 km s−1 amplitude across the cluster core, consistent with large-scale sloshing of the core gas. If the observed gas motions are isotropic, the kinetic pressure support is less than 10% of the thermal pressure support in the cluster core. The well-resolved, optically thin emission lines have Gaussian shapes, indicating that the turbulent driving scale is likely below 100 kpc, which is consistent with the size of the AGN jet inflated bubbles. We also report the first measurement of the ion temperature in the intracluster medium, which we find to be consistent with the electron temperature. In addition, we present a new measurement of the redshift of the brightest cluster galaxy NGC 1275.