116 research outputs found
Combined effects due to phase, intensity and contrast in electrooptic modulation. Application to ferroelectric materials
The combination of phase, intensity, and contrast effects during electrooptic
modulation is theoretically and exper- imentally investigated. One consequence
of this combination is the modification of the amplitude of the
single-frequency signals which are commonly used as working points for
electrooptic mod- ulators and for the measurements of the electrooptic
coefficients. Another consequence of direct intensity modulation is to shift
the double-frequency points of the transfer function from the positions they
normally occupy at the intensity extrema. They can even make them disappear if
the direct intensity modulation is stronger than the phase modulation. Such
phenomena are expected with any ferroelectric material in which a significant
part of the incident light is deflected or scattered by domain walls or grain
boundaries. They can lead to considerable mistakes in the determination of the
electrooptic coefficients. Appropriate procedures to extract the different
contributions are explained. Experimental results in rubidium hydrogen selenate
are given, and consequences of the working of electrooptic modulators are
discussed
Recursive internetwork architecture, investigating RINA as an alternative to TCP/IP (IRATI)
Driven by the requirements of the emerging applications and networks, the Internet has become an architectural patchwork of growing complexity which strains to cope with the changes. Mooreâs law prevented us from recognising that the problem does not hide in the high demands of todayâs applications but lies in the flaws of the Internetâs original design. The Internet needs to move beyond TCP/IP to prosper in the long term, TCP/IP has outlived its usefulness.
The Recursive InterNetwork Architecture (RINA) is a new Internetwork architecture whose fundamental principle is that networking is only interprocess communication (IPC). RINA reconstructs the overall structure of the Internet, forming a model that comprises a single repeating layer, the DIF (Distributed IPC Facility), which is the minimal set of components required to allow distributed IPC between application processes. RINA supports inherently and without the need of extra mechanisms mobility, multi-homing and Quality of Service, provides a secure and configurable environment, motivates for a more competitive marketplace and allows for a seamless adoption.
RINA is the best choice for the next generation networks due to its sound theory, simplicity and the features it enables. IRATIâs goal is to achieve further exploration of this new architecture. IRATI will advance the state of the art of RINA towards an architecture reference model and specifcations that are closer to enable implementations deployable in production scenarios.
The design and implemention of a RINA prototype on top of Ethernet will permit the experimentation and evaluation of RINA in comparison to TCP/IP. IRATI will use the OFELIA testbed to carry on its experimental activities. Both projects will benefit from the collaboration. IRATI will gain access to a large-scale testbed with a controlled network while OFELIA will get a unique use-case to validate the facility: experimentation of a non-IP based Internet
Compton-thick AGN in the NuSTAR Era. VIII. A joint NuSTAR-XMM-Newton Monitoring of the Changing-look Compton-thick AGN NGC 1358
We present the multi-epoch monitoring with NuSTAR and XMM-Newton of NGC 1358, a nearby Seyfert 2 galaxy whose properties made it a promising candidate X-ray changing-look active galactic nucleus (AGN), i.e., a source whose column density could transition from its 2017 Compton-thick (having LOS hydrogen column density NH,LOS> 1024cmâ2) state to a Compton-thin (NH,LOS< 1024cmâ2) one. The multi-epoch X-ray monitoring confirmed the presence of significant NH,LOSvariability over timescales of weeks to years, and allowed us to confirm the changing-look nature of NGC 1358, which has most recently been observed in a Compton-thin status. Multi-epoch monitoring with NuSTAR and XMM-Newton is demonstrated to be highly effective in simultaneously constraining three otherwise highly degenerate parameters: the torus average column density and covering factor, and the inclination angle between the torus axis and the observer. We find a tentative anticorrelation between column density and luminosity, which can be understood under the framework of chaotic cold accretion clouds driving recursive AGN feedback. The monitoring campaign of NGC 1358 has proven the efficiency of our newly developed method to select candidate NH,LOS-variable, heavily obscured AGN, which we plan to soon extend to a larger sample to better characterize the properties of the obscuring material surrounding accreting supermassive black holes, as well as to constrain AGN feeding models
The resolved scaling relations in DustPedia: Zooming in on the local Universe
We perform a homogeneous analysis of an unprecedented set of spatially
resolved scaling relations (SRs) between ISM components and other properties in
the range of scales 0.3-3.4 kpc. We also study some ratios: dust-to-stellar,
dust-to-gas, and dust-to-metal. We use a sample of 18 large, spiral, face-on
DustPedia galaxies. All the SRs are moderate/strong correlations except the
dust-HI SR that does not exist or is weak for most galaxies. The SRs do not
have a universal form but each galaxy is characterized by distinct
correlations, affected by local processes and galaxy peculiarities. The SRs
hold starting from 0.3 kpc, and if a breaking down scale exists it is < 0.3
kpc. By evaluating all galaxies at 3.4 kpc, differences due to peculiarities of
individual galaxies are cancelled out and the corresponding SRs are consistent
with those of whole galaxies. By comparing subgalactic and global scales, the
most striking result emerges from the SRs involving ISM components: the
dust-total gas SR is a good correlation at all scales, while the dust-H2 and
dust-HI SRs are good correlations at subkpc/kpc and total scales, respectively.
For the other explored SRs, there is a good agreement between small and global
scales and this may support the picture where the main physical processes
regulating the properties and evolution of galaxies occur locally. Our results
are consistent with the hypothesis of self-regulation of the SF process. The
analysis of subgalactic ratios shows that they are consistent with those
derived for whole galaxies, from low to high z, supporting the idea that also
these ratios could be set by local processes. Our results highlight the
heterogeneity of galaxy properties and the importance of resolved studies on
local galaxies in the context of galaxy evolution. They also provide
observational constraints to theoretical models and updated references for
high-z studies.Comment: 42 pages, 11 figures and 5 tables in the main text, 2 figures and 1
table in Appendix. Accepted for publication in A&
Expression of Human Beta-Defensins in Children with Chronic Inflammatory Bowel Disease
Background: Human beta-defensins (hBDs) are antimicrobial peptides known to play a major role in intestinal innate host defence. Altered mucosal expression of hBDs has been suggested to be implicated in chronic inflammatory bowel disease pathogenesis. However, little is known about expression of these peptides in children. Methods: Intestinal biopsies were obtained from the duodenum (n = 88), terminal ileum (n = 90) and ascending colon (n = 105) of children with Crohnâs disease (n = 26), ulcerative colitis (n = 11) and healthy controls (n = 16). Quantitative realtime (RT) PCR was performed and absolute mRNA copy numbers analyzed for hBD1-3 as well as inflammatory cytokines IL-8 and TNF-alpha. Results: Significant induction of hBD2 and hBD3 was observed in the inflamed terminal ileum and ascending colon of IBD children. In the ascending colon induction of hBD2 was found to be significantly lower in children with Crohnâs disease compared to ulcerative colitis. A strong correlation was found between inducible defensins hBD2 and 3 and the inflammatory cytokines IL-8 and TNF-alpha, both in the terminal ileum and ascending colon. Conclusion: Our study demonstrates distinct changes in hBD expression throughout the intestinal tract of children with IBD
Optical and mid-infrared line emission in nearby Seyfert galaxies
Line ratio diagnostics provide valuable clues on the source of ionizing
radiation in galaxies with intense black hole accretion and starbursting
events, such as local Seyfert or galaxies at the peak of the star formation
history. We aim to provide a reference joint optical and mid-IR analysis for
studying AGN identification via line ratios and testing predictions from
photoionization models. We obtained homogenous optical spectra with the
Southern Africa Large Telescope for 42 Seyfert galaxies with Spitzer/IRS
spectroscopy and X-ray to mid-IR multiband data available. After confirming the
power of the main optical ([OIII]) and mid-IR ([NeV], [OIV], [NeIII]) emission
lines in tracing AGN activity, we explore diagrams based on ratios of optical
and mid-IR lines by exploiting photoionization models of different ionizing
sources (AGN, star formation and shocks). We find that pure AGN photoionization
models are good at reproducing observations of Seyfert galaxies with an AGN
fractional contribution to the mid-IR (5-40 micron) emission larger than 50 per
cent. For targets with a lower AGN contribution these same models do not fully
reproduce the observed mid-IR line ratios. Mid-IR ratios like [NeV]/[NeII],
[OIV]/[NeII] and [NeIII]/[NeII] show a dependence on the AGN fractional
contribution to the mid-IR unlike optical line ratios. An additional source of
ionization, either from star formation or radiative shocks, can help explain
the observations in the mid-IR. Among combinations of optical and mid-IR
diagnostics in line ratio diagrams, only those involving the [OI]/Halpha ratio
are promising diagnostics for simultaneously unraveling the relative role of
AGN, star formation and, shocks. A proper identification of the dominant
ionizing source would require the exploitation of analysis tools based on
advanced statistical techniques as well as spatially resolved data.Comment: 31 pages, 15 figures, 2 tables. Accepted for publication in A&
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