221 research outputs found
Supersymmetry and R-symmetry breaking in models with non-canonical Kahler potential
We analyze several aspects of R-symmetry and supersymmetry breaking in
generalized O'Raifeartaigh models with non-canonical Kahler potential. Some
conditions on the Kahler potential are derived in order for the
non-supersymmetric vacua to be degenerate. We calculate the Coleman-Weinberg
(CW) effective potential for general quiral non-linear sigma models and then
study the 1-loop quantum corrections to the pseudo-moduli space. For
R-symmetric models, the quadratic dependence of the CW potential with the
ultraviolet cutoff scale disappears. We also show that the conditions for
R-symmetry breaking are independent of this scale and remain unchanged with
respect to those of canonical models. This is, R-symmetry can be broken when
generic R-charge assignments to the fields are made, while it remains unbroken
when only fields with R-charge 0 and 2 are present. We further show that these
models can keep the runaway behavior of their canonical counterparts and also
new runaway directions can be induced. Due to the runaway directions, the
non-supersymmetric vacua is metastable.Comment: 19 pages, revised version with minor changes, references added,
published in JHE
Mixing of porpoise ecotypes in southwestern UK waters revealed by genetic profiling
Contact zones between ecotypes are windows for understanding how species may react to climate changes. Here, we analysed the fine-scale genetic and morphological variation in harbour porpoises (Phocoena phocoena) around the UK by genotyping 591 stranded animals at nine microsatellite loci. The data were integrated with a prior study to map at high resolution the contact zone between two previously identified ecotypes meeting in the northern Bay of Biscay. Clustering and spatial analyses revealed that UK porpoises are derived from two genetic pools with porpoises from the southwestern UK being genetically differentiated, and having larger body sizes compared to those of other UK areas. Southwestern UK porpoises showed admixed ancestry between southern and northern ecotypes with a contact zone extending from the northern Bay of Biscay to the Celtic Sea and Channel. Around the UK, ancestry blends from one genetic group to the other along a southwest--northeast axis, correlating with body size variation, consistent with previously reported morphological differences between the two ecotypes. We also detected isolation by distance among juveniles but not in adults, suggesting that stranded juveniles display reduced intergenerational dispersal. The fine-scale structure of this admixture zone raises the question of how it will respond to future climate change and provides a reference point for further study
Terminal regions confer plasticity to the tetrameric assembly of human HspB2 and HspB3
Heterogeneity in small heat shock proteins (sHsps) spans multiple spatiotemporal regimes –
from fast fluctuations of part of the protein, to conformational variability of tertiary structure,
plasticity of the interfaces, and polydispersity of the inter-converting, and co-assembling
oligomers. This heterogeneity and dynamic nature of sHsps has significantly hindered their
structural characterisation. Atomic-coordinates are particularly lacking for vertebrate sHsps,
where most available structures are of extensively truncated homomers. sHsps play
important roles in maintaining protein levels in the cell and therefore in organismal health
and disease. HspB2 and HspB3 are vertebrate sHsps that are found co-assembled in
neuromuscular cells, and variants thereof are associated with disease. Here, we present the
structure of human HspB2/B3, which crystallised as a hetero-tetramer in a 3:1 ratio. In the
HspB2/B3 tetramer, the four a-crystallin domains (ACDs) assemble into a flattened
tetrahedron which is pierced by two non-intersecting approximate dyads. Assembly is
mediated by flexible “nuts and bolts” involving IXI/V motifs from terminal regions filling ACD
pockets. Parts of the N-terminal region bind in an unfolded conformation into the anti-parallel
shared ACD dimer grooves. Tracts of the terminal regions are not resolved, most likely due
to their disorder in the crystal lattice. This first structure of a full-length human sHsp
heteromer reveals the heterogeneous interactions of the terminal regions and suggests a
plasticity that is important for the cytoprotective functions of sHsps
Modeling magnetospheric fields in the Jupiter system
The various processes which generate magnetic fields within the Jupiter
system are exemplary for a large class of similar processes occurring at other
planets in the solar system, but also around extrasolar planets. Jupiter's
large internal dynamo magnetic field generates a gigantic magnetosphere, which
is strongly rotational driven and possesses large plasma sources located deeply
within the magnetosphere. The combination of the latter two effects is the
primary reason for Jupiter's main auroral ovals. Jupiter's moon Ganymede is the
only known moon with an intrinsic dynamo magnetic field, which generates a
mini-magnetosphere located within Jupiter's larger magnetosphere including two
auroral ovals. Ganymede's magnetosphere is qualitatively different compared to
the one from Jupiter. It possesses no bow shock but develops Alfv\'en wings
similar to most of the extrasolar planets which orbit their host stars within
0.1 AU. New numerical models of Jupiter's and Ganymede's magnetospheres
presented here provide quantitative insight into the processes that maintain
these magnetospheres. Jupiter's magnetospheric field is approximately
time-periodic at the locations of Jupiter's moons and induces secondary
magnetic fields in electrically conductive layers such as subsurface oceans. In
the case of Ganymede, these secondary magnetic fields influence the oscillation
of the location of its auroral ovals. Based on dedicated Hubble Space Telescope
observations, an analysis of the amplitudes of the auroral oscillations
provides evidence that Ganymede harbors a subsurface ocean. Callisto in
contrast does not possess a mini-magnetosphere, but still shows a perturbed
magnetic field environment. Callisto's ionosphere and atmospheric UV emission
is different compared to the other Galilean satellites as it is primarily been
generated by solar photons compared to magnetospheric electrons.Comment: Chapter for Book: Planetary Magnetis
Crystallographic reconstruction study of the effects of finish rolling temperature on the variant selection during bainite transformation in C-Mn high-strength steels
The effect of finish rolling temperature (FRT) on the austenite- ()
to-bainite () phase transformation is quantitatively investigated in
high-strength C-Mn steels. In particular, the present study aims to clarify the
respective contributions of the conditioning during the hot rolling and the
variant selection (VS) during the phase transformation to the inherited
texture. To this end, an alternative crystallographic reconstruction procedure,
which can be directly applied to experimental electron backscatter diffraction
(EBSD) mappings, is developed by combining the best features of the existing
models: the orientation relationship (OR) refinement, the local pixel-by-pixel
analysis and the nuclei identification and spreading strategy. The
applicability of this method is demonstrated on both quenching and partitioning
(Q&P) and as-quenched lath-martensite steels. The results obtained on the C-Mn
steels confirm that the sample finish rolled at the lowest temperature
(829{\deg}C) exhibits the sharpest transformation texture. It is shown that
this sharp texture is exclusively due to a strong VS from parent brass
{110}, S {213} and Goss {110} grains, whereas the VS from the
copper {112} grains is insensitive to the FRT. In addition, a
statistical VS analysis proves that the habit planes of the selected variants
do not systematically correspond to the predicted active slip planes using the
Taylor model. In contrast, a correlation between the Bain group to which the
selected variants belong and the FRT is clearly revealed, regardless of the
parent orientation. These results are discussed in terms of polygranular
accommodation mechanisms, especially in view of the observed development in the
hot-rolled samples of high-angle grain boundaries with misorientation axes
between and
Modification of forests by people means only 40% of remaining forests have high ecosystem integrity
Many global environmental agendas, including halting biodiversity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the scale and degree of forest modification remain poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate a globally consistent, continuous index of forest condition as determined by the degree of anthropogenic modification. Globally, only 17.4 million km2 of forest (40.5%) has high landscape-level integrity (mostly found in Canada, Russia, the Amazon, Central Africa, and New Guinea) and only 27% of this area is found in nationally designated protected areas. Of the forest inside protected areas, only 56% has high landscape-level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally
Data from a pre-publication independent replication initiative examining ten moral judgement effects
We present the data from a crowdsourced project seeking to replicate findings in independent laboratories before (rather than after) they are published. In this Pre-Publication Independent Replication (PPIR) initiative, 25 research groups attempted to replicate 10 moral judgment effects from a single laboratory's research pipeline of unpublished findings. The 10 effects were investigated using online/lab surveys containing psychological manipulations (vignettes) followed by questionnaires. Results revealed a mix of reliable, unreliable, and culturally moderated findings. Unlike any previous replication project, this dataset includes the data from not only the replications but also from the original studies, creating a unique corpus that researchers can use to better understand reproducibility and irreproducibility in science
The pipeline project: Pre-publication independent replications of a single laboratory's research pipeline
This crowdsourced project introduces a collaborative approach to improving the reproducibility of scientific research, in which findings are replicated in qualified independent laboratories before (rather than after) they are published. Our goal is to establish a non-adversarial replication process with highly informative final results. To illustrate the Pre-Publication Independent Replication (PPIR) approach, 25 research groups conducted replications of all ten moral judgment effects which the last author and his collaborators had “in the pipeline” as of August 2014. Six findings replicated according to all replication criteria, one finding replicated but with a significantly smaller effect size than the original, one finding replicated consistently in the original culture but not outside of it, and two findings failed to find support. In total, 40% of the original findings failed at least one major replication criterion. Potential ways to implement and incentivize pre-publication independent replication on a large scale are discussed
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