209 research outputs found
Genetic and genomic characterization of the LOP locus from Pilosella piloselloides subsp. Praealta : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science at Lincoln University
Apomixis is an asexual way of reproduction leading to the creation of clones of the mother plant. It is
controlled by two independent loci in Pilosella piloselloides subsp. Praealta (Hawkweed): LOA (Loss of
apomeiosis) and LOP (Loss of parthenogenesis), which are dominant. Apomictic plants develop one extremely
competitive genotype and spread it in a colonial strategy. Only a few crops are apomictic; however, the natural
creation of clones could considerably speed up the process of plant breeding and quickly stabilize new varieties
adapted to climate change. Pilosella is one of the model plants to study apomixis. The purpose of this work was
to investigate the LOP locus on a genetic and genomic level to better understand the mechanism of apomictic
plants in the hope of applying it to crops. Using a panel of deletion mutants, this study made it possible to
define the size of the LOP locus to about 650kb. A sequence of acceptable quality was checked for this locus
using BAC isolates. Finally, the PAR gene contained in the locus for parthenogenesis in Taraxacum (dandelion)
(Underwood et al., 2020) was sequenced in Pilosella and several species from the Asteraceae family, indicating
the level of conservation of the dominant allele compared to the recessive alleles
N=3 supersymmetric Born-Infeld theory
We construct an off-shell N=3 supersymmetric extension of the abelian D=4
Born-Infeld action starting from the action of supersymmetric Maxwell theory in
N=3 harmonic superspace. A crucial new feature of the N=3 super BI action is
that its interaction part contains only terms of the order 4k in the N=3
superfield strengths. The correct component bosonic BI action arises as the
result of elimination of auxiliary tensor field which is present in the
off-shell N=3 vector multiplet in parallel with the gauge field strength. In
this new Legendre-type representation, the bosonic BI action is fully specified
by a real function of the single variable quartic in the auxiliary tensor
field. The generic choice of this function amounts to a wide set of self-dual
nonlinear extensions of the Maxwell action. All of them admit an off-shell N=3
supersymmetrization.Comment: 18 pages, latex, no figures, slight changes, acknowledgements adde
Mixing in the Presence of Isosinglet Quarks
We analyse transitions in the framework of a minimal extension
of the Standard Model where either a or a isosinglet quark is
added to the standard quark spectrum. In the case of a isosinglet
quark, it is shown that there is a significant region of parameter space where
mixing is sufficiently enhanced to be observed at the next
round of experiments. On the contrary, in the case of a isosinglet
quark, it is pointed out that obtaining a substancial enhancement of mixing, while complying with the experimental constraints on rare
kaon decays, requires a contrived choice of parameters.Comment: 10 pages plus four figures. The figures are not included but are
available upon reques
COVID-19 in children with underlying chronic respiratory diseases: survey results from 174 centres
Background: Early reports suggest that most children infected with severe acute respiratory syndrome
coronavirus 2 (âSARS-CoV-2â) have mild symptoms. What is not known is whether children with chronic
respiratory illnesses have exacerbations associated with SARS-CoV-2 virus.
Methods: An expert panel created a survey, which was circulated twice (in April and May 2020) to
members of the Paediatric Assembly of the European Respiratory Society (ERS) and via the social media
of the ERS. The survey stratified patients by the following conditions: asthma, cystic fibrosis (CF),
bronchopulmonary dysplasia (BPD) and other respiratory conditions.
Results: In total 174 centres responded to at least one survey. 80 centres reported no cases, whereas 94
entered data from 945 children with coronavirus disease 2019 (COVID-19). SARS-CoV-2 was isolated
from 49 children with asthma of whom 29 required no treatment, 19 needed supplemental oxygen and
four children required mechanical ventilation. Of the 14 children with CF and COVID-19, 10 required no
treatment and four had only minor symptoms. Among the nine children with BPD and COVID-19, two
required no treatment, five required inpatient care and oxygen and two were admitted to a paediatric
intensive care unit (PICU) requiring invasive ventilation. Data were available from 33 children with other
conditions and SARS-CoV-2 of whom 20 required supplemental oxygen and 11 needed noninvasive or
invasive ventilation.
Conclusions: Within the participating centres, in children with asthma and CF, infection with SARS-CoV2 was well tolerated, but a substantial minority of children with BPD and other conditions required
ventilatory support indicating that these latter groups are at risk from SARS-CoV-2 infe
N=4 Supergravity Lagrangian for Type IIB Orientifold on T^6/Z_2 in Presence of Fluxes and D3-Branes
We derive the Lagrangian and the transformation laws of N=4 gauged
supergravity coupled to matter multiplets whose sigma-model of the scalars is
SU(1,1)/U(1)x SO(6,6+n)/SO(6)xSO(6+n) and which corresponds to the effective
Lagrangian of the Type IIB string compactified on the T^6/Z_2 orientifold with
fluxes turned on and in presence of n D3-branes. The gauge group is T^12 x G
where G is the gauge group on the brane and T^12 is the gauge group on the bulk
corresponding to the gauged translations of the R-R scalars coming from the R-R
four--form. The N=4 bulk sector of this theory can be obtained as a truncation
of the Scherk-Schwarz spontaneously broken N=8 supergravity. Consequently the
full bulk spectrum satisfies quadratic and quartic mass sum rules, identical to
those encountered in Scherk-Schwarz reduction gauging a flat group. This theory
gives rise to a no scale supergravity extended with partial super-Higgs
mechanism.Comment: 49 pages, LaTex, 2 figures. Misprints corrected, more comments adde
Complete breeding failures in ivory gull following unusual rainy storms in North Greenland
Natural catastrophic events such as heavy rainfall and windstorms may induce drastic decreases in breeding success of animal populations. We report the impacts of summer rainfalls on the reproductive success of ivory gull (Pagophila eburnea) in north-east Greenland. On two occasions, at Amdrup Land in July 2009 and at Station Nord in July 2011, we observed massive ivory gull breeding failures following violent rainfall and windstorms that hit the colonies. In each colony, all of the breeding birds abandoned their eggs or chicks during the storm. Juvenile mortality was close to 100% at Amdrup Land in 2009 and 100% at Station Nord in 2011. Our results show that strong winds associated with heavy rain directly affected the reproductive success of some Arctic bird species. Such extreme weather events may become more common with climate change and represent a new potential factor affecting ivory gull breeding success in the High Arctic
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Genetic drivers of kidney defects in the digeorge syndrome
BACKGROUND The DiGeorge syndrome, the most common of the microdeletion syndromes, affects multiple organs, including the heart, the nervous system, and the kidney. It is caused by deletions on chromosome 22q11.2; the genetic driver of the kidney defects is unknown. METHODS We conducted a genomewide search for structural variants in two cohorts: 2080 patients with congenital kidney and urinary tract anomalies and 22,094 controls. We performed exome and targeted resequencing in samples obtained from 586 additional patients with congenital kidney anomalies. We also carried out functional studies using zebrafish and mice. RESULTS We identified heterozygous deletions of 22q11.2 in 1.1% of the patients with congenital kidney anomalies and in 0.01% of population controls (odds ratio, 81.5; P = 4.5Ă1014). We localized the main drivers of renal disease in the DiGeorge syndrome to a 370-kb region containing nine genes. In zebrafish embryos, an induced loss of function in snap29, aifm3, and crkl resulted in renal defects; the loss of crkl alone was sufficient to induce defects. Five of 586 patients with congenital urinary anomalies had newly identified, heterozygous protein-Altering variants, including a premature termination codon, in CRKL. The inactivation of Crkl in the mouse model induced developmental defects similar to those observed in patients with congenital urinary anomalies. CONCLUSIONS We identified a recurrent 370-kb deletion at the 22q11.2 locus as a driver of kidney defects in the DiGeorge syndrome and in sporadic congenital kidney and urinary tract anomalies. Of the nine genes at this locus, SNAP29, AIFM3, and CRKL appear to be critical to the phenotype, with haploinsufficiency of CRKL emerging as the main genetic driver
A search for the decay
We search for the rare flavor-changing neutral-current decay in a data sample of 82 fb collected with the {\sl BABAR}
detector at the PEP-II B-factory. Signal events are selected by examining the
properties of the system recoiling against either a reconstructed hadronic or
semileptonic charged-B decay. Using these two independent samples we obtain a
combined limit of
at the 90% confidence level. In addition, by selecting for pions rather than
kaons, we obtain a limit of using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let
Measurement of the CP-Violating Asymmetry Amplitude sin2
We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.033 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.017 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes
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