4,062 research outputs found
Characterisation of a candidate dual AGN
We present Chandra and optical observations of a candidate dual AGN
discovered serendipitously while searching for recoiling black holes via a
cross-correlation between the serendipitous XMM source catalog (2XMMi) and
SDSS-DR7 galaxies with a separation no larger than ten times the sum of their
Petrosian radii. The system has a stellar mass ratio M/M. One of the galaxies (Source 1) shows clear evidence for AGN activity in
the form of hard X-ray emission and optical emission-line diagnostics typical
of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray
spectrum, bluer colours, and optical emission line ratios dominated by stellar
photoionisation with a "composite" signature, which might indicate the presence
of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII]
luminosity both nuclei fall within the locus defined by local Seyfert galaxies.
From the optical spectrum we estimate the electron densities finding n e cm and n e cm. From a 2D
decomposition of the surface brightness distribution we infer that both
galaxies host rotationally supported bulges (Sersic index ). While the
active nature of Source 1 can be established with confidence, whether the
nucleus of Source 2 is active remains a matter of debate. Evidence that a faint
AGN might reside in its nucleus is, however, tantalising.Comment: 16 pages, 9 figures. Accepted for publication on MNRAS. Comments
welcom
Testing the Tests: An Investigation into the Effectiveness of Alternative Assessment Methods for Bilingual Language-Impaired Children
Alternative language assessment procedures are gaining in prominence as authentic alternatives to traditional measures, but scant data exist regarding the relative effectiveness of the data they provide. This paper first summarizes the criteria for effective language assessment of bilingual children as documented in the literature, and then comparatively evaluates the effectiveness of research studies employing the three most-cited alternative assessment approaches: descriptive, dynamic, and curriculum-based. Conclusions regarding the impact of appropriate assessment on issues of over- and under-representation of bilingual Hispanic students are also discussed
Analisis Kadar Formaldehida Pada Peralatan Makan Melamin Yang Beredar Di Kota Manado
ANALISIS KADAR FORMALDEHIDA PADA PERALATAN MAKAN MELAMIN YANG BEREDAR DI KOTA MANADOMaria Getrudis Evelyn Lena1), Sri Sudewi1), Gayatri Citraningtyas1)1)Program Studi Farmasi FMIPA UNSRAT Manado, 95115 ABSTRACTFormaldehyde is a presertive agent that is often used in the medical world because it has antimicrobial properties, which can react with proteins so it can reduce the activity of microorganism. Formaldehyde is not allowed for use in foods. This study aims to determine the presence of formaldehyde compounds in melamin tableware circulating in Manado City. The identification of formaldehyde compounds was performerd by using reagent Nash characterized by the colour change of the solution to yellow. Determination of formaldehyde compound was done by UV-Vis spectrophotometry method at 410 nm wavelengths. The result showed that from two samples containing formaldehyde which sequentially increased concentration levels at minute 0 by 461.819, 613.523 ppm, respectively. This method has validity values that satisfy validation parameters so it can be accepted with correlation coefficient value of 0.9948; the average of recovery is 97.197%. The use of formaldehyde in melamin tableware exceeds the predetermined threshold according to the Food Grade ISO standard of 3 ppm.Keywords : Formaldehyde, melamine, UV-Vis spectrophotometry, Manado ABSTRAKFormaldehida adalah bahan pengawet yang sering digunakan dalam dunia kedokteran karena mempunyai sifat antimikroba yang dapat bereaksi dengan protein sehingga hal tersebut mengurangi aktivitas mikroorganisme. Formaldehida tidak diperbolehkan untuk digunakan pada makanan. Penelitian ini bertujuan untuk mengetahui keberadaan senyawa formaldehida pada peralatan makan melamin yang beredar di Kota Manado. Identifikasi senyawa formaldehida dilakukan dengan menggunakan pereaksi Nash yang ditandai dengan Perubahan warna larutan menjadi kuning. Penentuan kadar senyawa formaldehida dilakukan dengan metode spetrofotometri UV-Vis pada panjang gelombang 410 nm. Hasil penelitian menunjukkan bahwa dari enam sampel, terdapat lima sampel mengandung formaldehida yang secara berurutan mengalami kenaikan kadar konsentrasi pada menit ke 0 sebesar 461,819; 613,523; ppm. Metode ini memiliki nilai validitas yang memenuhi parameter validasi sehingga dapat diterima dengan nilai koefisien korelasi sebesar 0,9948, rata-rata perolehan kembali adalah 97,197% Penggunaan formaldehida dalam peralatan makan melamin melebihi ambang batas yang telah ditetapkan menurut standard Food Grade ISO yaitu 3 ppm
Hypercompact stellar clusters: morphological renditions and spectro-photometric models
Numerical relativity predicts that the coalescence of a black hole-binary
causes the newly formed black hole to recoil, and evidence for such recoils has
been found in the gravitational waves observed during the merger of
stellar-mass black holes. Recoiling (super)massive black holes are expected to
reside in hypercompact stellar clusters (HCSCs). Simulations of galaxy assembly
predict that hundreds of HCSCs should be present in the halo of a Milky
Way-type galaxy, and a fraction of those around the Milky Way should have
magnitudes within the sensitivity limit of existing surveys. However, recoiling
black holes and their HCSCs are still waiting to be securely identified. With
the goal of enabling searches through recent and forthcoming databases, we
improve over existing literature to produce realistic renditions of HCSCs bound
to black holes with a mass of 10 M. Including the effects of a
population of blue stragglers, we simulate their appearance in Pan-STARRS and
in forthcoming images. We also derive broad-band spectra and the
corresponding multi-wavelength colours, finding that the great majority of the
simulated HCSCs fall on the colour-colour loci defined by stars and galaxies,
with their spectra resembling those of giant K-type stars. We discuss the
clusters properties, search strategies, and possible interlopers.Comment: Accepted for publication on MNRAS, 17 pages, 7 figure
Alien Registration- Larlee, Lena G. (Medway, Penobscot County)
https://digitalmaine.com/alien_docs/8243/thumbnail.jp
Work fluctuations in bosonic Josephson junctions
We calculate the first two moments and full probability distribution of the work performed on a system of bosonic particles in a two-mode Bose-Hubbard Hamiltonian when the self-interaction term is varied instantaneously or with a finite-time ramp. In the instantaneous case, we show how the irreversible work scales differently depending on whether the system is driven to the Josephson or Fock regime of the bosonic Josephson junction. In the finite-time case, we use optimal control techniques to substantially decrease the irreversible work to negligible values. Our analysis can be implemented in present-day experiments with ultracold atoms and we show how to relate the work statistics to that of the population imbalance of the two modes
GRAVITY: The AO-Assisted, Two-Object Beam-Combiner Instrument
We present the proposal for the infrared adaptive optics (AO) assisted,
two-object, high-throughput, multiple-beam-combiner GRAVITY for the VLTI. This
instrument will be optimized for phase-referenced interferometric imaging and
narrow-angle astrometry of faint, red objects. Following the scientific
drivers, we analyze the VLTI infrastructure, and subsequently derive the
requirements and concept for the optimum instrument. The analysis can be
summarized with the need for highest sensitivity, phase referenced imaging and
astrometry of two objects in the VLTI beam, and infrared wavefront-sensing.
Consequently our proposed instrument allows the observations of faint, red
objects with its internal infrared wavefront sensor, pushes the optical
throughput by restricting observations to K-band at low and medium spectral
resolution, and is fully enclosed in a cryostat for optimum background
suppression and stability. Our instrument will thus increase the sensitivity of
the VLTI significantly beyond the present capabilities. With its two fibers per
telescope beam, GRAVITY will not only allow the simultaneous observations of
two objects, but will also push the astrometric accuracy for UTs to 10
micro-arcsec, and provide simultaneous astrometry for up to six baselines.Comment: 12 pages, to be published in the Proceedings of the ESO Workshop on
"The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd
Generation VLTI Instrumentation", eds. F. Paresce, A. Richichi, A. Chelli and
F. Delplancke, held in Garching, Germany, 4-8 April 200
- …