24,645 research outputs found
Chemical abundances of damped Lyman alpha systems in the XQ-100 survey
The XQ-100 survey has provided high signal-noise spectra of 100 redshift
3-4.5 quasars with the X-Shooter spectrograph. The metal abundances for 13
elements in the 41 damped Lyman alpha systems (DLAs) identified in the XQ-100
sample are presented, and an investigation into abundances of a variety of DLA
classes is conducted. The XQ-100 DLA sample contains five DLAs within 5000 km/s
of their host quasar (proximate DLAs; PDLAs) as well as three sightlines which
contain two DLAs within 10,000 km/s of each other along the same line-of-sight
(multiple DLAs; MDLAs). Combined with previous observations in the literature,
we demonstrate that PDLAs with logN(HI)<21.0 show lower [S/H] and [Fe/H]
(relative to intervening systems with similar redshift and N(HI)), whilst
higher [S/H] and [Si/H] are seen in PDLAs with logN(HI)>21.0. These abundance
discrepancies are independent of their line-of-sight velocity separation from
the host quasar, and the velocity width of the metal lines (v90). Contrary to
previous studies, MDLAs show no difference in [alpha/Fe] relative to single
DLAs matched in metallicity and redshift. In addition, we present follow-up
UVES data of J0034+1639, a sightline containing three DLAs, including a
metal-poor DLA with [Fe/H]=-2.82 (the third lowest [Fe/H] in DLAs identified to
date) at z=4.25. Lastly we study the dust-corrected [Zn/Fe], emphasizing that
near-IR coverage of X-Shooter provides unprecedented access to MgII, CaII and
TiII lines (at redshifts 3-4) to provide additional evidence for subsolar
[Zn/Fe] ratio in DLAs.Comment: Accepted to MNRAS. 19 pages plus Appendix material (102 pages total
Whole slide image registration for the study of tumor heterogeneity
Consecutive thin sections of tissue samples make it possible to study local
variation in e.g. protein expression and tumor heterogeneity by staining for a
new protein in each section. In order to compare and correlate patterns of
different proteins, the images have to be registered with high accuracy. The
problem we want to solve is registration of gigapixel whole slide images (WSI).
This presents 3 challenges: (i) Images are very large; (ii) Thin sections
result in artifacts that make global affine registration prone to very large
local errors; (iii) Local affine registration is required to preserve correct
tissue morphology (local size, shape and texture). In our approach we compare
WSI registration based on automatic and manual feature selection on either the
full image or natural sub-regions (as opposed to square tiles). Working with
natural sub-regions, in an interactive tool makes it possible to exclude
regions containing scientifically irrelevant information. We also present a new
way to visualize local registration quality by a Registration Confidence Map
(RCM). With this method, intra-tumor heterogeneity and charateristics of the
tumor microenvironment can be observed and quantified.Comment: MICCAI2018 - Computational Pathology and Ophthalmic Medical Image
Analysis - COMPA
Exclusive Double Charmonium Production from Decay
The exclusive decay of to a vector plus pseudoscalar charmonium is
studied in perturbative QCD. The corresponding branching ratios are predicted
to be of order for first three resonances, and we expect
these decay modes should be discovered in the prospective high-luminosity
facilities such as super experiment. As a manifestation of the
short-distance loop contribution, the relative phases among strong,
electromagnetic and radiative decay amplitudes can be deduced. It is
particularly interesting to find that the relative phase between strong and
electromagnetic amplitudes is nearly orthogonal. The resonance-continuum
interference effect for double charmonium production near various
resonances in annihilation is addressed
Separation of spin and charge in paired spin-singlet quantum Hall states
We propose a series of paired spin-singlet quantum Hall states, which exhibit
a separation of spin and charge degrees of freedom. The fundamental excitations
over these states, which have filling fraction \nu=2/(2m+1) with m an odd
integer, are spinons (spin-1/2 and charge zero) or fractional holons (charge
+/- 1/(2m+1) and spin zero). The braid statistics of these excitations are
non-abelian. The mechanism for the separation of spin and charge in these
states is topological: spin and charge excitations are liberated by binding to
a vortex in a p-wave pairing condensate. We briefly discuss related, abelian
spin-singlet states and possible transitions.Comment: 4 pages, uses revtex
GU Boo: A New 0.6 Msun Detached Eclipsing Binary
We have found a new low-mass, double-lined, detached eclipsing binary, GU
Boo, among a sample of new variables from the ROTSE-I database. The binary has
an orbital period of 0.488728 +/- 0.000002 days, and estimated apparent
magnitudes Vrotse = 13.7 and I = 11.8. Our analysis of the light and radial
velocity curves of the system yields individual masses and radii of M1= 0.610
+/- 0.007 Msun, M2 = 0.599 +/- 0.006 Msun, R1= 0.623 +/- 0.016 Rsun, R2= 0.620
+/- 0.020 Rsun. The stars in GU Boo are therefore very similar to the
components of the eclipsing binary YY Gem. For this study we have adopted a
mean effective temperature for the binary of Teff = 3870 +/- 130 K. Based on
its space velocities we suggest that GU Boo is a main sequence binary, possibly
with an age of several Gyr. The metallicity of the binary is not well
constrained at this point but we speculate that it should not be very different
from solar. We have compared the physical parameters of GU Boo with current
low-mass stellar models, where we accounted for uncertainties in age and
metallicity by considering a wide range of values for those parameters. Our
comparisons reveal that all the models underestimate the radii of the
components of GU Boo by at least 10-15%. This result is in agreement with the
recent studies of YY Gem and CU Cnc.Comment: 41 pages, 10 figures, 11 tables; accepted by Ap
Dominance and GĂE interaction effects improvegenomic prediction and genetic gain inintermediate wheatgrass (Thinopyrumintermedium)
Genomic selection (GS) based recurrent selection methods were developed to accelerate the domestication of intermediate wheatgrass [IWG, Thinopyrum intermedium (Host) Barkworth & D.R. Dewey]. A subset of the breeding population phenotyped at multiple environments is used to train GS models and then predict trait values of the breeding population. In this study, we implemented several GS models that investigated the use of additive and dominance effects and GĂE interaction effects to understand how they affected trait predictions in intermediate wheatgrass. We evaluated 451 genotypes from the University of Minnesota IWG breeding program for nine agronomic and domestication traits at two Minnesota locations during 2017â2018. Genet-mean based heritabilities for these traits ranged from 0.34 to 0.77. Using fourfold cross validation, we observed the highest predictive abilities (correlation of 0.67) in models that considered GĂE effects. When GĂE effects were fitted in GS models, trait predictions improved by 18%, 15%, 20%, and 23% for yield, spike weight, spike length, and free threshing, respectively. Genomic selection models with dominance effects showed only modest increases of up to 3% and were trait-dependent. Crossenvironment predictions were better for high heritability traits such as spike length, shatter resistance, free threshing, grain weight, and seed length than traits with low heritability and large environmental variance such as spike weight, grain yield, and seed width. Our results confirm that GS can accelerate IWG domestication by increasing genetic gain per breeding cycle and assist in selection of genotypes with promise of better performance in diverse environments
LOW ENERGY SUPERSYMMETRY PHENOMENOLOGY
We summarize the current status and future prospects for low energy (weak
scale) supersymmetry. In particular, we evaluate the capabilities of various
, and colliders to discover evidence for supersymmetric
particles. Furthermore, assuming supersymmetry is discovered, we discuss
capabilities of future facilities to dis-entangle the anticipated spectrum of
super-particles, and, via precision measurements, to test mass and coupling
parameters for comparison with various theoretical expectations. We comment
upon the complementarity of proposed hadron and machines for a
comprehensive study of low energy supersymmetry.Comment: 74 page (Latex) file; a PS or uuencoded manuscript with embedded
figures is available via anonymous ftp at
ftp://hep.fsu.edu/preprints/baer/FSUHEP950401.ps or .uu . Contributed chapter
to DPF study group on Electroweak Symmetry Breaking and Beyond the Standard
Model
Single Top Quark Production via FCNC Couplings at Hadron Colliders
We calculate single top-quark production at hadron colliders via the
chromo-magnetic flavor-changing neutral current couplings and . We find that the strength for the anomalous ()
coupling may be probed to () at the Tevatron with of data and
() at the LHC with of data. The two couplings may be
distinguished by a comparision of the single top signal with the direct top and
top decay signals for these couplings.Comment: 18 pages, 6 figures, 3 table
Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide
Tin perovskites have emerged as promising alternatives to toxic lead perovskites in next-generation photovoltaics, but their poor environmental stability remains an obstacle towards more competitive performances. Therefore, a full understanding of their decomposition processes is needed to address these stability issues. Herein, we elucidate the degradation mechanism of 2D/3D tin perovskite films based on (PEA)0.2(FA)0.8SnI3 (where PEA is phenylethylammonium and FA is formamidinium). We show that SnI4, a product of the oxygen-induced degradation of tin perovskite, quickly evolves into iodine via the combined action of moisture and oxygen. We identify iodine as a highly aggressive species that can further oxidise the perovskite to more SnI4, establishing a cyclic degradation mechanism. Perovskite stability is then observed to strongly depend on the hole transport layer chosen as the substrate, which is exploited to tackle film degradation. These key insights will enable the future design and optimisation of stable tin-based perovskite optoelectronics
Cosmological evolution of interacting phantom (quintessence) model in Loop Quantum Gravity
The dynamics of interacting dark energy model in loop quantum cosmology (LQC)
is studied in this paper. The dark energy has a constant equation of state
and interacts with dark matter through a form . We
find for quintessence model () the cosmological evolution in LQC is the
same as that in classical Einstein cosmology; whereas for phantom dark energy
(), although there are the same critical points in LQC and classical
Einstein cosmology, loop quantum effect reduces significantly the parameter
spacetime () required by stability. If parameters and satisfy
the conditions that the critical points are existent and stable, the universe
will enter an era dominated by dark energy and dark matter with a constant
energy ratio between them, and accelerate forever; otherwise it will enter an
oscillatory regime. Comparing our results with the observations we find at
confidence level the universe will accelerate forever.Comment: 15 pages, 8 figures, to appear in JCA
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