Ultra-Luminous X-ray Sources: Evidence for Very Efficient Formation of Population III Stars Contributing to the Cosmic Near-Infrared Background Excess?

Accumulating evidence indicates that some of ultra-luminous X-ray sources (ULXs) are intermediate mass black holes (IMBHs), but the formation process of IMBHs is unknown. One possibility is that they were formed as remnants of population III (Pop III) stars, but it has been thought that the probability of being an ULX is too low for IMBHs distributed in galactic haloes to account for the observed number of ULXs. Here we show that the number of ULXs can be explained by such halo IMBHs passing through a dense molecular cloud, if Pop III star formation is very efficient as recently suggested by the excess of the cosmic near-infrared background radiation that cannot be accounted for by normal galaxy populations. We calculate the luminosity function of X-ray sources in our scenario and find that it is consistent with observed data. Our scenario can explain that ULXs are preferentially found at outskirts of large gas concentrations in star forming regions. A few important physical effects are pointed out and discussed, including gas dynamical friction, radiative efficiency of accretion flow, and radiative feedback to ambient medium. ULXs could last for ~10^{5-6} yr to emit a total energy of ~10^{53} erg, which is sufficient to power the ionized expanding nebulae found by optical observations.Comment: 6 pages, 1 figures, accepted to ApJ main journal, with extended discussions. Main conclusions unchange

Detection of exchange interaction in STM measurements through Fanolike interference effects

We address Fano-like interference effects in scanning tunneling microscopy (STM) measurements of nanoscale systems, e.g. two-level systems. Common for these systems is that second order tunneling contributions give rise to interference effects that cause suppressed transmission through the system for certain energies. The suppressed transmission is measurable either in the differential conductance or in the bias voltage derivative thereof.Comment: 9 pages, 3 figures, submitted: in addition to the results published in Phys. Rev. B, 75, 153309 (2007), this paper contains a more thorough discussion on the used transport formalism, studies of asymmetric couplings to the substrate, and discussion of non-resonant levels. The non-resonant case is related to spin-dependent tunnelin

Vibrational assignments and line shapes in inelastic tunnelling spectroscopy: H on Cu(100)

We have carried out a computational study of the inelastic electron tunneling spectrum (IETS) of the two vibrational modes of a single hydrogen atom on a Cu(100) surface in a scanning tunneling microscopy (STM) junction. This study addresses key issues about vibrational assignment and line shape of observed peaks in IETS within the framework of density functional theory calculations and the Lorente-Persson theory for STM-IETS. We argue that the observation of only a single, broad peak in the STM-IETS [L.J. Lauhon and W. Ho, Phys. Rev. Lett. 85, 4566 (2000)] is not caused by any symmetry restrictions or any cancellation between inelastic and elastic vibrational contributions for one of the two modes but is due to strongly overlapping superposition of the contributions from the two modes caused by the rather large instrumental broadening and the narrow vibrational energy separation between the modes. In particular, we find that this broadening and the large asymmetry of the vibrational line shapes gives rise to substantial apparent vibrational energy shifts of the two modes and decrease their apparent energy separation

Occurrence of Enzyme Systems for Production and Decomposition of Oxalate in a White-Rot Fungus Coriolus versicolor and Some Characteristics of Glyoxylate Oxidase

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Studi Perbandingan Back Propogation

Keberhasilan pemahaman tentang bagaimana membuat komputer belajar akan membuka banyak manfaat baru dari komputer. Sebuah pemahaman yang rinci tentang algoritma pengolahan informasi untuk pembelajaran mesin dapat membuat pemahaman yang sebaik kemampuan belajar manusia. Banyak jenis pembelajaran mesin yang kita tahu, beberapa diantaranya adalah Backpropagation (BP), Extreme Learning Machine (ELM), dan Support Vector Machine (SVM). Penelitian ini menggunakan lima data yang memiliki beberapa karakteristik. Hasil penelitian ini, dari ketiga model yang diamati memberikan akurasi klasifikasi yang sebanding. Penelitian ini memiliki tiga kesimpulan, yang terbaik dalam akurasi adalah BP, yang terbaik dalam stabilitas adalah SVM dan CPU time terbaik adalah ELM untuk data bioinformatika

Relation between inelastic electron tunneling and vibrational excitation of single adsorbates on metal surfaces

We analyse theoretically a relation between the vibrational generation rate of a single adsorbate by tunneling electrons and the inelastic tunneling (IET) current in scanning tunneling microscope, and the influence of the vibrational excitations on the rate of adsorbate motions. Special attention is paid to the effects of finite lifetime of the vibrational excitations. We show that in the vicinity and below the IET threshold the rate of adsorbate motion deviates from a simple power-law dependence on the bias voltage due to the effects of bath temperature and adsorbate vibrational lifetime broadenings. The temperature broadening appears to be confined near the threshold voltage within a narrow region of several $k_B T$, whereas the lifetime broadening manifests itself in a much wider region of applied voltages below the IET threshold.Comment: 8 pages including 4 figure

Establishment of a patient-derived orthotopic Xenograft (PDOX) model of HER-2-positive cervical cancer expressing the clinical metastatic pattern.

Squamous cell carcinoma of the cervix, highly prevalent in the developing world, is often metastatic and treatment resistant with no standard treatment protocol. Our laboratory pioneered the patient-derived orthotopic xenograft (PDOX) nude mouse model with the technique of surgical orthotopic implantation (SOI). Unlike subcutaneous transplant patient-derived xenograft (PDX) models, PDOX models metastasize. Most importantly, the metastasis pattern correlates to the patient. In the present report, we describe the development of a PDOX model of HER-2-positive cervical cancer. Metastasis after SOI in nude mice included peritoneal dissemination, liver metastasis, lung metastasis as well as lymph node metastasis reflecting the metastatic pattern in the donor patient. Metastasis was detected in 4 of 6 nude mice with primary tumors. Primary tumors and metastases in the nude mice had histological structures similar to the original tumor and were stained by an anti-HER-2 antibody in the same pattern as the patient's cancer. The metastatic pattern, histology and HER-2 tumor expression of the patient were thus preserved in the PDOX model. In contrast, subcutaneous transplantation of the patient's cervical tumors resulted in primary growth but not metastasis

Inelastic effects in electron transport studied with wave packet propagation

A time-dependent approach is used to explore inelastic effects during electron transport through few-level systems. We study a tight-binding chain with one and two sites connected to vibrations. This simple but transparent model gives insight about inelastic effects, their meaning and the approximations currently used to treat them. Our time-dependent approach allows us to trace back the time sequence of vibrational excitation and electronic interference, the ibrationally introduced time delay and the electronic phase shift. We explore a full range of parameters going from weak to strong electron-vibration coupling, from tunneling to contact, from one-vibration description to the need of including all vibrations for a correct description of inelastic effects in transport. We explore the validity of single-site resonant models as well as its extension to more sites via molecular orbitals and the conditions under which multi-orbital, multi-vibrational descriptions cannot be simplified. We explain the physical meaning of the spectral features in the second derivative of the electron current with respect to the bias voltage. This permits us to nuance the meaning of the energy value of dips and peaks. Finally, we show that finite-band effects lead to electron back-scattering off the molecular vibrations in the regime of high-conductance, although the drop in conductance at the vibrational threshold is rather due to the rapid variation of the vibronic density of states.Comment: 38 pages, 14 figure

Inelastic transport theory from first-principles: methodology and applications for nanoscale devices

We describe a first-principles method for calculating electronic structure, vibrational modes and frequencies, electron-phonon couplings, and inelastic electron transport properties of an atomic-scale device bridging two metallic contacts under nonequilibrium conditions. The method extends the density-functional codes SIESTA and TranSIESTA that use atomic basis sets. The inelastic conductance characteristics are calculated using the nonequilibrium Green's function formalism, and the electron-phonon interaction is addressed with perturbation theory up to the level of the self-consistent Born approximation. While these calculations often are computationally demanding, we show how they can be approximated by a simple and efficient lowest order expansion. Our method also addresses effects of energy dissipation and local heating of the junction via detailed calculations of the power flow. We demonstrate the developed procedures by considering inelastic transport through atomic gold wires of various lengths, thereby extending the results presented in [Frederiksen et al., Phys. Rev. Lett. 93, 256601 (2004)]. To illustrate that the method applies more generally to molecular devices, we also calculate the inelastic current through different hydrocarbon molecules between gold electrodes. Both for the wires and the molecules our theory is in quantitative agreement with experiments, and characterizes the system-specific mode selectivity and local heating.Comment: 24 pages, 17 figure

Nonequilibrium resonant spectroscopy of molecular vibrons

Quantum transport through single molecules is essentially affected by molecular vibrations. We investigate the behavior of the prototype single-level model with intermediate electron-vibron coupling and arbitrary coupling to the leads. We have developed a theory which allows to explore this regime via the nonequilibrium Green function formalism. We show that the nonequilibrium resonant spectroscopy is able to determine the energies of molecular orbitals and the spectrum of molecular vibrations. Our results are relevant to scanning tunneling spectroscopy experiments, and demonstrate the importance of the systematic and self-consistent investigation of the effects of the vibronic dynamics onto the transport through single molecules.Comment: 4 pages, 5 figures, submitte