6,671 research outputs found
The architectural patronage of the FÄáčimid queen-mother DurzÄn (d. 385/995): an interdisciplinary analysis of literary sources, material evidence and historical context
This paper on FÄáčimid female architectural patronage is divided into two parts. The first contains an analysis of the link between historical sources and epigraphic evidence, the second interprets such evidence in the light of the political and economic climates in which such patronage took place. The figure this paper focuses on is DurzÄn. She was the consort of the FÄáčimid imam-caliph al-Muâizz (r. 341-365/953-975) and mother of his successor, the imam-caliph al-âAzÄ«z (r. 365-386/975-996) and the first and most prolific of the FÄáčimid patronesses
Optimized White Reflectance in Photonic Network Structures
Three-dimensional disordered networks are receiving increasing attention as
versatile architectures for highly scattering materials. However, due to their
complex morphology, little is still known about the interplay between their
structural and optical properties. Here, we describe a simple algorithm that
allows to generate photonic network structures inspired by that of the
Cyphochilus beetle, famous for the bright white reflectance of its thin
cuticular scales. The model allows to vary the degree of structural anisotropy
and filling fraction of the network independently, revealing the key
contribution of these two parameters to the overall scattering efficiency.
Rigorous numerical simulations show that the obtained structures can exceed the
broadband reflectance of the beetle while using less material, providing new
insights for the design of advanced scattering materials.Comment: 10 pages, 3 figures. peer reviewed version, published in final form
at https://doi.org/10.1002/adom.20190004
A New Perspective on Clustered Planarity as a Combinatorial Embedding Problem
The clustered planarity problem (c-planarity) asks whether a hierarchically
clustered graph admits a planar drawing such that the clusters can be nicely
represented by regions. We introduce the cd-tree data structure and give a new
characterization of c-planarity. It leads to efficient algorithms for
c-planarity testing in the following cases. (i) Every cluster and every
co-cluster (complement of a cluster) has at most two connected components. (ii)
Every cluster has at most five outgoing edges.
Moreover, the cd-tree reveals interesting connections between c-planarity and
planarity with constraints on the order of edges around vertices. On one hand,
this gives rise to a bunch of new open problems related to c-planarity, on the
other hand it provides a new perspective on previous results.Comment: 17 pages, 2 figure
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). II. Constraints on star formation in ram-pressure stripped gas
Context: Several galaxies in the Virgo cluster are known to have large HI gas
tails related to a recent ram-pressure stripping event. The Virgo cluster has
been extensively observed at 1539 A in the far-ultraviolet for the GALEX
Ultraviolet Virgo Cluster Survey (GUViCS), and in the optical for the Next
Generation Virgo Survey (NGVS), allowing a study of the stellar emission
potentially associated with the gas tails of 8 cluster members. On the
theoretical side, models of ram-pressure stripping events have started to
include the physics of star formation. Aim: We aim to provide quantitative
constraints on the amount of star formation taking place in the ram-pressure
stripped gas, mainly on the basis of the far-UV emission found in the GUViCS
images in relation with the gas content of the tails. Methods: We have
performed three comparisons of the young stars emission with the gas column
density: visual, pixel-by-pixel and global. We have compared our results to
other observational and theoretical studies. Results: We find that the level of
star formation taking place in the gas stripped from galaxies by ram-pressure
is low with respect to the available amount of gas. Star formation is lower by
at least a factor 10 compared to the predictions of the Schmidt Law as
determined in regular spiral galaxy disks. It is also lower than measured in
dwarfs galaxies and the outer regions of spirals, and than predicted by some
numerical simulations. We provide constraints on the star formation efficiency
in the ram-pressure stripped gas tails, and compare these with current models.Comment: Accepted in A&A, 17 pages (including the appendix and "on-line"
figures of the paper
A Variational Formulation of Symplectic Noncommutative Mechanics
The standard lore in noncommutative physics is the use of first order
variational description of a dynamical system to probe the space
noncommutativity and its consequences in the dynamics in phase space. As the
ultimate goal is to understand the inherent space noncommutativity we propose a
variational principle for noncommutative dynamical systems in configuration
space, based on results of our previous work [14]. We hope that this
variational formulation in configuration space can be of help to elucidate the
definition of some global and dynamical properties of classical and quantum
noncommutative space.Comment: 17 pages, Latex. Accepted for publication in IJGMM
Morphological characterisation of malignant histiocytosis in a cat
Malignant histiocytosis (MH) is a progressive systemic neoplastic proliferation
of morphologically atypical histiocytes, well characterised in humans and dogs
but only recently identified in the cat. In all species, liver, lung, lymph nodes,
spleen and bone marrow are infiltrated by atypical histiocytes, and the disease
is rapidly fatal. The purpose of this study was to describe the clinical, histological,
immunohistochemical and ultrastructural findings of MH in a cat, together
with the diagnostic work-up and a list of differential diagnoses. Clinical evaluation
included a complete blood-cell count, serum biochemistry, urinalysis, serology
and ultrasound examination. The cat had clinical signs of depression,
thinness, dehydration, pale mucous membranes and tachycardia. Abdominal
ultrasonography revealed generalised splenomegaly and hepatomegaly. Necroscopy
showed whitish nodules, randomly scattered throughout the parenchyma
in the spleen and liver. The periportal lymph nodes were greatly enlarged
and the cut surface was uniformly greyish-white and translucent. Histological
examination revealed pleomorphic proliferation of large round tumour
cells, with numerous phagocytic vacuoles containing erytrocytes, leukocytes
and haemosiderin. By immunohistochemistry, positivity for lysozyme and
α1-antitrypsin and a scattered positivity for Mac 387 were observed. Ultrastructural
features of tumour cells included cytoplasmic lipid droplets, lysosomes and
phagolysosomes. MH in the cat needs to be differentiated from diffuse granulomatous
disease, non-Hodgkin’s lymphoma and Hodgkin’s-like disease. The
morphological features of the tumour cells, combined with immunohistochemical
and ultrastructural observation, are consistent with a diagnosis of MH in
the cat
The effect of the environment on the HI scaling relations
We use a volume-, magnitude-limited sample of nearby galaxies to investigate
the effect of the environment on the HI scaling relations. We confirm that the
HI-to-stellar mass ratio anti correlates with stellar mass, stellar mass
surface density and NUV-r colour across the whole range of parameters covered
by our sample (10^9 <M*<10^11 Msol, 7.5 <mu*<9.5 Msol kpc^-2, 2<NUV-r<6 mag).
These scaling relations are also followed by galaxies in the Virgo cluster,
although they are significantly offset towards lower gas content.
Interestingly, the difference between field and cluster galaxies gradually
decreases moving towards massive, bulge-dominated systems. By comparing our
data with the predictions of chemo-spectrophotometric models of galaxy
evolution, we show that starvation alone cannot explain the low gas content of
Virgo spirals and that only ram-pressure stripping is able to reproduce our
findings. Finally, motivated by previous studies, we investigate the use of a
plane obtained from the relations between the HI-to-stellar mass ratio, stellar
mass surface density and NUV-r colour as a proxy for the HI deficiency
parameter. We show that the distance from the `HI gas fraction plane' can be
used as an alternative estimate for the HI deficiency, but only if carefully
calibrated on pre-defined samples of `unperturbed' systems.Comment: Accepted for publication on MNRAS main journal. 11 pages, 6 figures,
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