Subpixel Spatial Resolution of the X-Ray Charge-Coupled Device Based on the Charge Cloud Shape

When an X-ray photon lands into a pixel (event pixel), the primary charge is mainly collected into the event pixel. If the X-ray landing position is sufficiently close to the pixel boundary, the primary charge spills over to the adjacent pixel forming split events. We can easily understand that there are three parameters coupled together; the X-ray landing position inside the pixel, the X-ray event pattern and the primary charge cloud shape. We can determine any one of them from the other two parameters. Since we know the charge cloud shape using the multi-pitch mesh experiment, we can calculate the X-ray landing position with subpixel resolution using the event pattern. We applied our method to Ti-K X-rays for the charge-coupled device with $12 \mu$m square pixel. Once the primary charge splits into the adjacent pixel, we can determine the X-ray landing position with subpixel resolution. Using three- or four-pixel split events, we can determine the X-ray landing position with an accuracy of less than $1 \mu$m. For a two-pixel split event, we obtained a similar position accuracy in the split direction with no improvement in the direction perpendicular to it. We will discuss the type of CCD which can achieve the subpixel resolution for the entire area of the CCD.Comment: 16pages, 5 figures. To appear in Jpn. J. Appl. Phys. March, 200

Nonthermal emission properties of the northwestern rim of supernova remnant RX J0852-4622

The supernova remnant (SNR) RX J0852-4622 (Vela Jr., G266.6-1.2) is one of the most important SNRs for investigating the acceleration of multi-TeV particles and the origin of Galactic cosmic rays because of its strong synchrotron X-ray and TeV gamma-ray emission, which show a shell-like morphology similar to each other. Using the XMM-Newton archival data consisting of multiple pointing observations of the northwestern rim of the remnant, we investigate the spatial properties of the nonthermal X-ray emission as a function of distance from an outer shock wave. All X-ray spectra are well reproduced by an absorbed power-law model above 2 keV. It is found that the spectra show gradual softening from a photon index 2.56 in the rim region to 2.96 in the interior region. We show that this radial profile can be interpreted as a gradual decrease of the cutoff energy of the electron spectrum due to synchrotron cooling. By using a simple spectral evolution model that includes continuous synchrotron losses, the spectral softening can be reproduced with the magnetic field strength in the post-shock flow to less than several tens of uG. If this is a typical magnetic field in the SNR shell, gamma-ray emission would be accounted for by inverse Compton scattering of high-energy electrons that also produce the synchrotron X-ray emission. Future hard X-ray imaging observations with Nustar and ASTRO-H and TeV gamma-ray observations with the Cherenkov Telescope Array (CTA) will allow to us to explore other possible explanations of the systematic softening of the X-ray spectra.Comment: accepted by A&

Exploring Fine Subpixel Spatial Resolution of Hybrid CMOS Detectors

When an X-ray is incident onto the silicon absorber array of a detector, it liberates a large number of electrons, which tend to diffuse outward into what is referred to as the charge cloud. This number can vary from tens to thousands across the soft X-ray bandpass (0.1 - 10 keV). The charge cloud can then be picked up by several pixels, and forms a specific pattern based on the exact incident location of the X-ray. We present experimental results on subpixel resolution for a custom H2RG with 36 micron pixels, presented in Bray 2018, and compare the data to simulated images . We then apply the model simulation to a prototype small pixel hybrid CMOS detector (HCD) that would be suitable for the Lynx X-ray surveyor. We also discuss the ability of a small pixel detector to obtain subpixel resolution

Histone H3 lysine 56 acetylation by Rtt109 is crucial for chromosome positioning

Peer reviewedPublisher PD

TFIIIC Localizes Budding Yeast ETC Sites to the Nuclear Periphery

Peer reviewedPublisher PD

Overabundance of Calcium in the young SNR RX J0852−-4622: evidence of over-production of 44^{44}Ti

Recently, COMPTEL has detected $\gamma$-rays of 1157 keV from $^{44}$Ti in the direction of the SNR RX J0852$-$4622 (Iyudin et al. 1998). Since $^{44}$Ti is a product of explosive nucleosynthesis and its half lifetime \tau\sb{1/2} is about 60 yrs, RX J0852$-$4622 must be a young supernova remnant and radiation is dominated by the ejecta rather than by interstellar matter. We have detected an X-ray emission line at $4.1\pm 0.2$ keV which is thought to come from highly ionized Ca. The emission line is so far only seen in the north-west shell region of RX J0852$-$4622. The X-ray spectrum can be well fitted with that of thin hot plasma of cosmic abundances except that of Ca, which is overabundant by a factor of $8 \pm 5$. Assuming that most of Ca is $^{44}$Ca, which originates from $^{44}$Ti by radioactive decay, we estimate a total Ca mass of about $1.1\times 10^{-3}M_\odot$. Combining the amount of $^{44}$Ca and the observed flux of the $^{44}$Ti $\gamma$-ray line, the age of RX J0852$-$4622 is around 1000 yrs.Comment: 14 pages, 5figures, accepted for publication of PAS

Vacancy Ordering in Vanadium Carbides Based on V_6C_5

The ordered arrangement of carbon vacancies in vanadium carbides near V_6C_5 has been analysed by means of selected-area electron diffraction and high-voltage electron microscopy. A new type of ordered distribution of carbon vacancies is found at non-stoichiometric compositions between V_6C_5 and V_8C_7. This structure can be expressed as a long-period structure consisting of the enantiomorphic domains based on the structure V_6C_5 which was determined by Billingham, Bell and Lewis (1972). The periodic domain boundaries with spacing eleven times the nearest-neighbour interatomic distance are directly observed by electron microscopy

The Interplay of Metaphor and Iconicity: A Cognitive Approach to Poetic Texts

This essay attempts to clarify the interrelationship between the notions of metaphor and iconicity in the theory of cognitive metaphor, particularly in the model of ‘blending’ (Turner and Fauconnier 1995, in press, Fauconnier and Turner 1996, Turner 1996, 1998, among others). In cognitive and semiotic terms, ‘icons’ and ‘metaphors’ share that property of signification ‘motivated’ by similarity. Connecting things of similarity is one of the basic operations of the human mind. The treatment of metaphor and iconicity in an interrelated fashion will provide a more cohesive and integrated explanation of various linguistic phenomena. The list of such phenomena includes word formation, word order, grammaticalisation, semantic change, poetic discourse, signed languages and writing systems, as manifestations of the interplay between metaphor and iconicity. This study shows that poetic texts, in particular, serve as an optimal example in this exploration because in poetic discourse, the interplay of metaphor and iconicity is foregrounded rather than backgrounded as in everyday discourse (Jakobson and Waugh 1979). This paper, therefore, aims to contribute in the following two issues. Firstly, theoretical clarification of the interplay of metaphor and iconicity will be given in cognitive terms. Particularly, with the model of blending, we can specify which part(s) of the metaphorical process - whether the input, generic, or blended spaces - relate(s) to the iconic mapping of form and meaning. Secondly, the analysis will demonstrate how the interplay of metaphor and iconicity is manifested in linguistic signs in general, and in poetic texts in particular. It will be claimed that there are two major types of manifestation: (i) that there are iconic moments in metaphor; and (ii) that a form acquires an iconic meaning via metaphor