1,560 research outputs found
Application potential of cold neutron radiography in plant science research
Though comprehensive knowledge of water status and water flow are important prerequisites for plant in many aspects of modern plant science truly non-destructive methods for the in-situ study of water transport are rare. Advanced imaging methods such as Magnetic Resonance Imaging (MRI) or Cold Neutron Radiography (CNR) may be applied to fill this gap. In CNR strong interaction of cold neutrons with hydrogen provides a high contrast even for small amounts of water. The combination of CNR with the low-contrast tracer D2O allows the direct visualisation of water flow and the calculation of water flow rates in plants with a high resolution at the tissue level. Here, we give a general introduction into this method, describe their latest developments, report about studies applying neutron radiography in plant science and provide most recent results of our experiments in this field
Pseudoconvex domains spread over complex homogeneous manifolds
Using the concept of inner integral curves defined by Hirschowitz we
generalize a recent result by Kim, Levenberg and Yamaguchi concerning the
obstruction of a pseudoconvex domain spread over a complex homogeneous manifold
to be Stein. This is then applied to study the holomorphic reduction of
pseudoconvex complex homogeneous manifolds X=G/H. Under the assumption that G
is solvable or reductive we prove that X is the total space of a G-equivariant
holomorphic fiber bundle over a Stein manifold such that all holomorphic
functions on the fiber are constant.Comment: 21 page
On hyperbolicity of SU(2)-equivariant, punctured disc bundles over the complex affine quadric
Given a holomorphic line bundle over the complex affine quadric , we
investigate its Stein, SU(2)-equivariant disc bundles. Up to equivariant
biholomorphism, these are all contained in a maximal one, say .
By removing the zero section to one obtains the unique Stein,
SU(2)-equivariant, punctured disc bundle over which contains entire
curves. All other such punctured disc bundles are shown to be Kobayashi
hyperbolic.Comment: 15 pages, v2: minor changes, to appear in Transformation Group
Special biconformal changes of K\"ahler surface metrics
The term "special biconformal change" refers, basically, to the situation
where a given nontrivial real-holomorphic vector field on a complex manifold is
a gradient relative to two K\"ahler metrics, and, simultaneously, an
eigenvector of one of the metrics treated, with the aid of the other, as an
endomorphism of the tangent bundle. A special biconformal change is called
nontrivial if the two metrics are not each other's constant multiples. For
instance, according to a 1995 result of LeBrun, a nontrivial special
biconformal change exists for the conformally-Einstein K\"ahler metric on the
two-point blow-up of the complex projective plane, recently discovered by Chen,
LeBrun and Weber; the real-holomorphic vector field involved is the gradient of
its scalar curvature. The present paper establishes the existence of nontrivial
special biconformal changes for some canonical metrics on Del Pezzo surfaces,
viz. K\"ahler-Einstein metrics (when a nontrivial holomorphic vector field
exists), non-Einstein K\"ahler-Ricci solitons, and K\"ahler metrics admitting
nonconstant Killing potentials with geodesic gradients.Comment: 16 page
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Alterations in sperm long RNA contribute to the epigenetic inheritance of the effects of postnatal trauma
Abstract: Psychiatric diseases have a strong heritable component known to not be restricted to DNA sequence-based genetic inheritance alone but to also involve epigenetic factors in germ cells. Initial evidence suggested that sperm RNA is causally linked to the transmission of symptoms induced by traumatic experiences. Here, we show that alterations in long RNA in sperm contribute to the inheritance of specific trauma symptoms. Injection of long RNA fraction from sperm of males exposed to postnatal trauma recapitulates the effects on food intake, glucose response to insulin and risk-taking in adulthood whereas the small RNA fraction alters body weight and behavioural despair. Alterations in long RNA are maintained after fertilization, suggesting a direct link between sperm and embryo RNA
Hamiltonian 2-forms in Kahler geometry, III Extremal metrics and stability
This paper concerns the explicit construction of extremal Kaehler metrics on
total spaces of projective bundles, which have been studied in many places. We
present a unified approach, motivated by the theory of hamiltonian 2-forms (as
introduced and studied in previous papers in the series) but this paper is
largely independent of that theory.
We obtain a characterization, on a large family of projective bundles, of
those `admissible' Kaehler classes (i.e., the ones compatible with the bundle
structure in a way we make precise) which contain an extremal Kaehler metric.
In many cases, such as on geometrically ruled surfaces, every Kaehler class is
admissible. In particular, our results complete the classification of extremal
Kaehler metrics on geometrically ruled surfaces, answering several
long-standing questions.
We also find that our characterization agrees with a notion of K-stability
for admissible Kaehler classes. Our examples and nonexistence results therefore
provide a fertile testing ground for the rapidly developing theory of stability
for projective varieties, and we discuss some of the ramifications. In
particular we obtain examples of projective varieties which are destabilized by
a non-algebraic degeneration.Comment: 40 pages, sequel to math.DG/0401320 and math.DG/0202280, but largely
self-contained; partially replaces and extends math.DG/050151
Monilochaetes and allied genera of the Glomerellales, and a reconsideration of families in the Microascales
We examined the phylogenetic relationships of two species that mimic
Chaetosphaeria in teleomorph and anamorph morphologies,
Chaetosphaeria tulasneorum with a Cylindrotrichum
anamorph and Australiasca queenslandica with a Dischloridium
anamorph. Four data sets were analysed: a) the internal transcribed spacer
region including ITS1, 5.8S rDNA and ITS2 (ITS), b) nc28S (ncLSU) rDNA, c)
nc18S (ncSSU) rDNA, and d) a combined data set of ncLSU-ncSSU-RPB2 (ribosomal
polymerase B2). The traditional placement of Ch. tulasneorum in the
Microascales based on ncLSU sequences is unsupported and
Australiasca does not belong to the Chaetosphaeriaceae. Both
holomorph species are nested within the Glomerellales. A new genus,
Reticulascus, is introduced for Ch. tulasneorum with
associated Cylindrotrichum anamorph; another species of
Reticulascus and its anamorph in Cylindrotrichum are
described as new. The taxonomic structure of the Glomerellales is
clarified and the name is validly published. As delimited here, it includes
three families, the Glomerellaceae and the newly described
Australiascaceae and Reticulascaceae. Based on ITS and ncLSU
rDNA sequence analyses, we confirm the synonymy of the anamorph genera
Dischloridium with Monilochaetes. Consequently
Dischloridium laeënse, type species of the genus, and three
related species are transferred to the older genus Monilochaetes. The
teleomorph of D. laeënse is described in Australiasca
as a new species. The Plectosphaerellaceae, to which the anamorph
genus Stachylidium is added, is basal to the Glomerellales
in the three-gene phylogeny. Stilbella annulata also belongs to this
family and is newly combined in Acrostalagmus. Phylogenetic analyses
based on ncLSU, ncSSU, and combined ncLSU-ncSSU-RPB2 sequences clarify family
relationships within the Microascales. The family
Ceratocystidaceae is validated as a strongly supported monophyletic
group consisting of Ceratocystis, Cornuvesica,
Thielaviopsis, and the type species of Ambrosiella. The new
family Gondwanamycetaceae, a strongly supported sister clade to the
Ceratocystidaceae, is introduced for the teleomorph genus
Gondwanamyces and its Custingophora anamorphs. Four families
are accepted in the Microascales, namely the
Ceratocystidaceae, Gondwanamycetaceae,
Halosphaeriaceae, and Microascaceae. Because of a suggested
affinity of a Faurelina indica isolate to the Microascales,
the phylogenetic position of the Chadefaudiellaceae is reevaluated.
Based on the results from a separate ncLSU analysis of the
Dothideomycetes, Faurelina is excluded from the
Microascales and placed in the Pleosporales
A systematic autopsy survey of human infant bridging veins
In the first years of life, subdural haemorrhage (SDH) within the cranial cavity can occur through accidental and non-accidental mechanisms as well as from birth-related injury. This type of bleeding is the most common finding in victims of abusive head trauma (AHT). Historically, the most frequent cause of SDHs in infancy is suggested to be traumatic damage to bridging veins traversing from the brain to the dural membrane. However, several alternative hypotheses have been suggested for the cause and origin of subdural bleeding. It has also been suggested by some that bridging veins are too large to rupture through the forces associated with AHT. To date, there have been no systematic anatomical studies on infant bridging veins. During 43 neonatal, infant and young child post-mortem examinations, we have mapped the locations and numbers of bridging veins onto a 3D model of the surface of a representative infant brain. We have also recorded the in situ diameter of 79 bridging veins from two neonatal, one infant and two young children at post-mortem examination. Large numbers of veins, both distant from and directly entering the dural venous sinuses, were discovered travelling between the brain and dural membrane, with the mean number of veins per brain being 54.1 and the largest number recorded as 94. The mean diameter of the bridging veins was 0.93 mm, with measurements ranging from 0.05 to 3.07 mm. These data demonstrate that some veins are extremely small and subjectively, and they appear to be delicate. Characterisation of infant bridging veins will contribute to the current understanding of potential vascular sources of subdural bleeding and could also be used to further develop computational models of infant head injury
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