2,189 research outputs found
Normalization of ortophotos based on no-change pixels using Multivariate Alteration Detection (MAD)
A Critique of Personas as representations of "the other" in Cross-Cultural Technology Design
A literature review on cross-cultural personas reveals both, a trend in projects lacking accomplishment and personas reinforcing previous biases. We first suggest why failures or incompleteness may have ensued, while then we entice a thoughtful alteration of the design process by creating and validating personas together with those that they embody. Personas created in people's own terms support the design of technologies by truly satisfying users' needs and drives. Examining the experiences of those working "out there", and our practises, we conclude persona is a vital designerly artefact to empowering people in representing themselves. A persona-based study on User-Created Persona in Namibia contrasts the current persona status-quo via an ongoing co-design effort with urban and rural non-designers. However we argue persona as a design device must ease its implicit colonial tendency to and impulses in depicting "the other". Instead we endorse serenity, mindfulness and local enabling in design at large and in the African context in particular
A possible bias on the estimate of Lbol/Ledd in AGN as a function of luminosity and redshift
The BH mass (and the related Eddington ratio) in broad line AGN is usually
evaluated by combining estimates (often indirect) of the BLR radius and of the
FWHM of the broad lines, under the assumption that the BLR clouds are in
Keplerian motion around the BH. Such an evaluation depends on the geometry of
the BLR. There are two major options for the BLR configuration: spherically
symmetric or ``flattened''. In the latter case the inclination to the line of
sight becomes a relevant parameter. This paper is devoted to evaluate the bias
on the estimate of the Eddington ratio when a spherical geometry is assumed
(more generally when inclination effects are ignored), while the actual
configuration is ``flattened'', as some evidence suggests. This is done as a
function of luminosity and redshift, on the basis of recent results which show
the existence of a correlation between the fraction of obscured AGN and these
two parameters up to at least z=2.5. The assumed BLR velocity field is akin to
the ``generalized thick disk'' proposed by Collin et al. (2006). Assuming an
isotropic orientation in the sky, the mean value of the bias is calculated as a
function of luminosity and redshift. It is demonstrated that, on average, the
Eddington ratio obtained assuming a spherical geometry is underestimated for
high luminosities, and overestimated for low luminosities. This bias converges
for all luminosities at z about 2.7, while nothing can be said on this bias at
larger redshifts due to the lack of data. The effects of the bias, averaged
over the luminosity function of broad line AGN, have been calculated. The
results imply that the bias associated with the a-sphericity of the BLR make
even worse the discrepancy between the observations and the predictions of
evolutionary models.Comment: 6 pages, 3 figures, accepted for publication in A&
Spectroscopy of Broad Line Blazars from 1LAC
We report on optical spectroscopy of 165 Flat Spectrum Radio Quasars (FSRQs)
in the Fermi 1LAC sample, which have helped allow a nearly complete study of
this population. Fermi FSRQ show significant evidence for non-thermal emission
even in the optical; the degree depends on the gamma-ray hardness. They also
have smaller virial estimates of hole mass than the optical quasar sample. This
appears to be largely due to a preferred (axial) view of the gamma-ray FSRQ and
non-isotropic (H/R ~ 0.4) distribution of broad-line velocities. Even after
correction for this bias, the Fermi FSRQ show higher mean Eddington ratios than
the optical population. A comparison of optical spectral properties with Owens
Valley Radio Observatory radio flare activity shows no strong correlation.Comment: Accepted for publication in Ap
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
We study the low-contrast Fe II emission blends in the ultraviolet
(1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC
5548 and show that these features vary in flux and that these variations are
correlated with those of the optical continuum. The amplitude of variability of
the optical Fe II emission is 50% - 75% that of Hbeta and the ultraviolet Fe II
emission varies with an even larger amplitude than Hbeta. However, accurate
measurement of the flux in these blends proves to be very difficult even using
excellent Fe II templates to fit the spectra. We are able to constrain only
weakly the optical Fe II emission-line response timescale to a value less than
several weeks; this upper limit exceeds all the reliably measured emission-line
lags in this source so it is not particularly meaningful. Nevertheless, the
fact that the optical Fe II and continuum flux variations are correlated
indicates that line fluorescence in a photoionized plasma, rather than
collisional excitation, is responsible for the Fe II emission. The iron
emission templates are available upon request.Comment: 34 pages including 12 figures and 2 tables. Accepted for publication
by ApJ (tentatively in vol. 626 June 10, 2005
The blazar S5 0014+813: a real or apparent monster?
A strong hard X-ray luminosity from a blazar flags the presence of a very
powerful jet. If the jet power is in turn related to the mass accretion rate,
the most luminous hard X-ray blazars should pinpoint the largest accretion
rates, and therefore the largest black hole masses. These ideas are confirmed
by the Swift satellite observations of the blazar S5 0014+813, at the redshift
z=3.366. Swift detected this source with all its three instruments, from the
optical to the hard X-rays. Through the construction of its spectral energy
distribution we are confident that its optical-UV emission is thermal in
origin. Associating it to the emission of a standard optically thick
geometrically thin accretion disk, we find a black hole mass of 40 billion
solar masses, radiating at 40% the Eddington value. The derived mass is among
the largest ever found. Super-Eddington slim disks or thick disks with the
presence of a collimating funnel can in principle reduce the black hole mass
estimate, but tends to produce spectra bluer than observed.Comment: 5 pages, 2 figures, accepted for publication as a letter in MNRAS
after minor revisio
The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]: no evidence for Eddington-limited sources
There have been recent claims that a significant fraction of type 2 AGN
accrete close or even above the Eddington limit. In type 2 AGN the bolometric
luminosity (L_b) is generally inferred from the [OIII] emission line luminosity
(L_OIII). The key issue, in order to estimate the bolometric luminosity in
these AGN, is therefore to know the bolometric correction to be applied to
L_OIII. A complication arises from the fact that the observed L_OIII is
affected by extinction, likely due to dust within the narrow line region. The
extinction-corrected [OIII] luminosity (L^c_OIII) is a better estimator of the
nuclear luminosity than L_OIII. However, so far only the bolometric correction
to be applied to the uncorrected L_OIII has been evaluated. This paper is
devoted to estimate the bolometric correction C_OIII=L_b/L^c_OIII in order to
derive the Eddington ratios for the type 2 AGN in a sample of SDSS objects. We
have collected from the literature 61 sources with reliable estimate of both
L^c_OIII and X-ray luminosities (L_X). To estimate C_OIII, we combined the
observed correlation between L^c_OIII and L_X with the X-ray bolometric
correction. We found, contrary to previous studies, a linear correlation
between L^c_OIII and L_X. We estimated C_OIII using the luminosity-dependent
X-ray bolometric correction of Marconi et al. (2004), and we found a mean value
of C_OIII in the luminosity ranges log L_OIII=38-40, 40-42, and 42-44 of 87,
142 and 454 respectively. We used it to calculate the Eddington ratio
distribution of type 2 SDSS AGN at 0.3<z<0.4 and we found that these sources
are not accreting near their Eddington limit, contrary to previous claims.Comment: 8 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
Reverberation Mapping Results from MDM Observatory
We present results from a multi-month reverberation mapping campaign
undertaken primarily at MDM Observatory with supporting observations from
around the world. We measure broad line region (BLR) radii and black hole
masses for six objects. A velocity-resolved analysis of the H_beta response
shows the presence of diverse kinematic signatures in the BLR.Comment: To appear in the Proceedings of the IAU Symposium No. 267:
Co-Evolution of Central Black Holes and Galaxies, Rio de Janeiro, 200
Touch me not
Central Poststroke Pain syndrome (CPSP) can occur due to disruption of the somatosensory pathways of the brain at any level such as the thalamus, medulla, or cerebral cortex. It is characterized by sensory abnormalities and hyperesthesia in the part of the body correlating to the central lesion. The treatment of this pain syndrome is often difficult, and it does not usually respond to traditional analgesics. The first line of treatment is drugs aimed at lowering neuronal hyperexcitability, for example, amitriptyline or lamotrigine, with gabapentin considered a second line
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