2,752 research outputs found
A submillimeter interference spectrometer - Characteristics, performance and measurements
Performance characteristics of interference spectrometer using submillimeter wave
Suzaku Confirms NGC~3660 is an Unabsorbed Seyfert 2
An enigmatic group of objects, unabsorbed Seyfert 2s may have intrinsically
weak broad line regions, obscuration in the line of sight to the BLR but not to
the X-ray corona, or so much obscuration that the X-ray continuum is completely
suppressed and the observed spectrum is actually scattered into the line of
sight from nearby material. NGC 3660 has been shown to have weak broad
optical/near infrared lines, no obscuration in the soft X-ray band, and no
indication of "changing look" behavior. The only previous hard X-ray detection
of this source by Beppo-SAX seemed to indicate that the source might harbor a
heavily obscured nucleus. However, our analysis of a long-look Suzaku
observation of this source shows that this is not the case, and that this
source has a typical power law X-ray continuum with normal reflection and no
obscuration. We conclude that NGC 3660 is confirmed to have no unidentified
obscuration and that the anomolously high Beppo-SAX measurement must be due to
source confusion or similar, being inconsistent with our Suzaku measurements as
well as non-detections from Swift-BAT and RXTE.Comment: Accepted to PAS
Power-law tails from multiplicative noise
We show that the well-known Langevin equation, modeling the Brownian motion
and leading to a Gaussian stationary distribution of the corresponding
Fokker-Planck equation, is changed by the smallest multiplicative noise. This
leads to a power-law tail of the distribution at large enough momenta. At
finite ratio of the correlation strength for the multiplicative and additive
noise the stationary energy distribution becomes exactly the Tsallis
distribution.Comment: 4 pages, LaTeX, revtex4 style, 2 figure
Quantum rotor description of the Mott-insulator transition in the Bose-Hubbard model
We present the novel approach to the Bose-Hubbard model using the
quantum rotor description. The effective action formalism
allows us to formulate a problem in the phase only action and obtain an
analytical formulas for the critical lines. We show that the nontrivial
phase field configurations have an impact on the phase
diagrams. The topological character of the quantum field is governed by terms
of the integer charges - winding numbers. The comparison presented results to
recently obtained quantum Monte Carlo numerical calculations suggests that the
competition between quantum effects in strongly interacting boson systems is
correctly captured by our model.Comment: accepted to PR
The Creation of Defects with Core Condensation
Defects in superfluid 3He, high-Tc superconductors, QCD colour superfluids
and cosmic vortons can possess (anti)ferromagnetic cores, and their
generalisations. In each case there is a second order parameter whose value is
zero in the bulk which does not vanish in the core. We examine the production
of defects in the simplest 1+1 dimensional scalar theory in which a second
order parameter can take non-zero values in a defect core. We study in detail
the effects of core condensation on the defect production mechanism.Comment: 9 pages, 7 figures, small corrections, 2 references added, final
version to be published in PR
Synchrotron Radiation Induced X-Ray Microanalysis: A Realistic Alternative for Electron- and Ion-Beam Microscopy?
Synchrotron radiation induced X-ray micro fluorescence analysis (μ-SRXRF) is compared with more conventional microanalytical techniques such as secondary ion microscopy (SIMS) and electron probe X-ray microanalysis (EPXMA) for two typical microanalytical applications. μ-SRXRF and EPXMA are employed for the analysis of individual particles, showing the complementary character of both techniques. By means of element mapping of trace constituents in a heterogeneous feldspar material, the strong and weak points of μ-SRXRF in comparison to EPXMA and SIMS are illustrated. The most striking difference between μ-SRXRF and the other two microanalytical methods is the ability of SRXRF to probe deep into the investigated material, whereas SIMS and EPXMA only investigate the upper surface of the material. The possibilities of μ-SRXRF using radiation from bending magnets of third generation synchrotron rings are briefly discussed. μ-SRXRF is considered to be a valuable method for the analysis of major, minor and trace elements which can be used profitably m parallel with electron-and ion-beam methods
Hydrogen Permeability of Polymer Matrix Composites at Cryogenic Temperatures
This paper presents experimental methods and results of an ongoing study of the correlation between damage state and hydrogen gas permeability of laminated composite materials under mechanical strains and thermal loads. A specimen made from IM-7/977-2 composite material has been mechanically cycled at room temperature to induce microcrack damage. Crack density and tensile modulus were observed as functions of number of cycles. Damage development was found to occur most quickly in the off-axis plies near the outside of the laminate. Permeability measurements were made after 170,000 cycles and 430,000 cycles. Leak rate was found to depend on applied mechanical strain, crack density, and test temperature
Measuring workplace bullying
Workplace bullying is increasingly being recognized as a serious problem in society today; it is
also a problem that can be difficult to define and evaluate accurately. Research in this area has been
hampered by lack of appropriate measurement techniques. Social scientists can play a key part in
tackling the phenomenon of workplace bullying by developing and applying a range of research
methods to capture its nature and incidence in a range of contexts. We review current methods of
research into the phenomenon of bullying in the workplace. We examine definitional issues,
including the type, frequency, and duration of bullying acts, and consider the role of values and
norms of the workplace culture in influencing perception and measurement of bullying behavior. We
distinguish methods that focus on: (a) inside perspectives on the experience of bullying (including
questionnaires and surveys, self-report through diary-keeping, personal accounts through interviews,
focus groups and critical incident technique, and projective techniques such as bubble dialogue); (b)
outside perspectives (including observational methods and peer nominations); (c) multi-method
approaches that integrate both inside and outside perspectives (including case studies). We suggest
that multi-method approaches may offer a useful way forward for researchers and for practitioners
anxious to assess and tackle the problem of bullying in their organizations.CIFPEC/CIEC - Centro de Investigação em Estudos da Criança, UM (UI 644 e 317 da FCT)
NuSTAR and XMM-NEWTON Observations of NGC 1365: Extreme Absorption Variability and a Constant Inner Accretion Disk
We present a spectral analysis of four coordinated NuSTAR+XMM-Newton observations of the Seyfert galaxy NGC 1365. These exhibit an extreme level of spectral variability, which is primarily due to variable line-of-sight absorption, revealing relatively unobscured states in this source for the first time. Despite the diverse range of absorption states, each of the observations displays the same characteristic signatures of relativistic reflection from the inner accretion disk. Through time-resolved spectroscopy, we find that the strength of the relativistic iron line and the Compton reflection hump relative to the intrinsic continuum are well correlated, which is expected if they are two aspects of the same broadband reflection spectrum. We apply self-consistent disk reflection models to these time-resolved spectra in order to constrain the inner disk parameters, allowing for variable, partially covering absorption to account for the vastly different absorption states that were observed. Each of the four observations is treated independently to test the consistency of the results obtained for the black hole spin and the disk inclination, which should not vary on observable timescales. We find both the spin and the inclination determined from the reflection spectrum to be consistent, confirming that NGC 1365 hosts a rapidly rotating black hole; in all cases the dimensionless spin parameter is constrained to be a* > 0.97 (at 90% statistical confidence or better
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