1,530 research outputs found
Nodal and planar cell polarity signaling cooperate to regulate zebrafish convergence and extension gastrulation movements
During vertebrate gastrulation, convergence and extension (C and E) of the primary anteroposterior (AP) embryonic axis is driven by polarized mediolateral (ML) cell intercalations and is influenced by AP axial patterning. Nodal signaling is essential for patterning of the AP axis while planar cell polarity (PCP) signaling polarizes cells with respect to this axis, but how these two signaling systems interact during C and E is unclear. We find that the neuroectoderm of Nodal-deficient zebrafish gastrulae exhibits reduced C and E cell behaviors, which require Nodal signaling in both cell- and non-autonomous fashions. PCP signaling is partially active in Nodal-deficient embryos and its inhibition exacerbates their C and E defects. Within otherwise naïve zebrafish blastoderm explants, however, Nodal induces C and E in a largely PCP-dependent manner, arguing that Nodal acts both upstream of and in parallel with PCP during gastrulation to regulate embryonic axis extension cooperatively
Family matters: infants, toddlers and preschoolers of parents affected by mental illness
Contains fulltext :
102540.pdf (publisher's version ) (Open Access)One in five young people in Australia, including infants, toddlers and preschoolers, lives in a family with a parent with a mental illness.1 Families affected by mental illness are more likely than other families to experience poverty and social isolation,2 and are more likely to have children taken into care.3
A combination of factors influences the child’s risk of psychopathology. These include psychosocial adversity, the child’s developmental status and age, genetics, family relationships, the severity and chronicity of parental psychiatric disorder, comorbidity, and the involvement of other carers in the child’s life. Not all children whose parents have mental health problems will experience difficulties themselves.4
Parental diagnosis itself does not confer risk, and many parents with severe depression, schizophrenia and other disorders are adequate caregivers.5 Rather, it is the severity and chronicity of psychopathology and the variation in parental personality, genetic characteristics, coping style and social circumstances that confer risk. Children’s characteristics, such as temperament and sex, can also influence the parent–child relationship and parenting behaviour.6
This article outlines the impact of three key mental health disorders on parenting and young offspring, and describes implications for practice
Isospin-Violating Meson-Nucleon Vertices as an Alternate Mechanism of Charge-Symmetry Breaking
We compute isospin-violating meson-nucleon coupling constants and their
consequent charge-symmetry-breaking nucleon-nucleon potentials. The couplings
result from evaluating matrix elements of quark currents between nucleon states
in a nonrelativistic constituent quark model; the isospin violations arise from
the difference in the up and down constituent quark masses. We find, in
particular, that isospin violation in the omega-meson--nucleon vertex dominates
the class IV CSB potential obtained from these considerations. We evaluate the
resulting spin-singlet--triplet mixing angles, the quantities germane to the
difference of neutron and proton analyzing powers measured in elastic
scattering, and find them commensurate to those computed
originally using the on-shell value of the - mixing amplitude.
The use of the on-shell - mixing amplitude at has been
called into question; rather, the amplitude is zero in a wide class of models.
Our model possesses no contribution from - mixing at , and
we find that omega-meson exchange suffices to explain the measured
analyzing power difference~at~183 MeV.Comment: 20 pages, revtex, 3 uuencoded PostScript figure
Progressive transformation of a flux rope to an ICME
The solar wind conditions at one astronomical unit (AU) can be strongly
disturbed by the interplanetary coronal mass ejections (ICMEs). A subset,
called magnetic clouds (MCs), is formed by twisted flux ropes that transport an
important amount of magnetic flux and helicity which is released in CMEs. At 1
AU from the Sun, the magnetic structure of MCs is generally modeled neglecting
their expansion during the spacecraft crossing. However, in some cases, MCs
present a significant expansion. We present here an analysis of the huge and
significantly expanding MC observed by the Wind spacecraft during 9 and 10
November, 2004. After determining an approximated orientation for the flux rope
using the minimum variance method, we precise the orientation of the cloud axis
relating its front and rear magnetic discontinuities using a direct method.
This method takes into account the conservation of the azimuthal magnetic flux
between the in- and out-bound branches, and is valid for a finite impact
parameter (i.e., not necessarily a small distance between the spacecraft
trajectory and the cloud axis). Moreover, using the direct method, we find that
the ICME is formed by a flux rope (MC) followed by an extended coherent
magnetic region. These observations are interpreted considering the existence
of a previous larger flux rope, which partially reconnected with its
environment in the front. These findings imply that the ejected flux rope is
progressively peeled by reconnection and transformed to the observed ICME (with
a remnant flux rope in the front part).Comment: Solar Physics (in press
Homologous Flares and Magnetic Field Topology in Active Region NOAA 10501 on 20 November 2003
We present and interpret observations of two morphologically homologous
flares that occurred in active region (AR) NOAA 10501 on 20 November 2003. Both
flares displayed four homologous H-alpha ribbons and were both accompanied by
coronal mass ejections (CMEs). The central flare ribbons were located at the
site of an emerging bipole in the center of the active region. The negative
polarity of this bipole fragmented in two main pieces, one rotating around the
positive polarity by ~ 110 deg within 32 hours. We model the coronal magnetic
field and compute its topology, using as boundary condition the magnetogram
closest in time to each flare. In particular, we calculate the location of
quasiseparatrix layers (QSLs) in order to understand the connectivity between
the flare ribbons. Though several polarities were present in AR 10501, the
global magnetic field topology corresponds to a quadrupolar magnetic field
distribution without magnetic null points. For both flares, the photospheric
traces of QSLs are similar and match well the locations of the four H-alpha
ribbons. This globally unchanged topology and the continuous shearing by the
rotating bipole are two key factors responsible for the flare homology.
However, our analyses also indicate that different magnetic connectivity
domains of the quadrupolar configuration become unstable during each flare, so
that magnetic reconnection proceeds differently in both events.Comment: 24 pages, 10 figures, Solar Physics (accepted
- …