524 research outputs found
Large Bi-2212 single crystal growth by the floating-zone technique
Effects of the growth velocity on the crystal growth behavior of
Bi_2Sr_2Ca_1Cu_2O_x (Bi-2212) have been studied by floating zone technique. The
results show that a necessary condition for obtaining large single crystals
along the c-axis is that the solid-liquid interface of a growing rod maintains
a stable planar growth front. The planar liquid-solid growth interface tends to
break down into a cellular interface, while the growth velocity is higher than
0.25 mm/h. Single crystals of up to 50x7.2x7 mm3 along the a-, b- and caxes
have been cut in a 7.2 mm diameter rod with optimum growth conditions. Tconset
is 91 K measured by magnetic properties measurement system (MPMS) for as-grown
crystals. Optical polarization microscope and neutron diffraction show that the
quality of the single crystals is good.Comment: 5 pages, 4 figure
Radiative Corrections to Double Dalitz Decays: Effects on Invariant Mass Distributions and Angular Correlations
We review the theory of meson decays to two lepton pairs, including the cases
of identical as well as non-identical leptons, as well as CP-conserving and
CP-violating couplings. A complete lowest-order calculation of QED radiative
corrections to these decays is discussed, and comparisons of predicted rates
and kinematic distributions between tree-level and one-loop-corrected
calculations are presented for both pi-zero and K-zero decays.Comment: 25 pages, 18 figures, added figures and commentar
Towards Activity Context using Software Sensors
Service-Oriented Computing delivers the promise of configuring and
reconfiguring software systems to address user's needs in a dynamic way.
Context-aware computing promises to capture the user's needs and hence the
requirements they have on systems. The marriage of both can deliver ad-hoc
software solutions relevant to the user in the most current fashion. However,
here it is a key to gather information on the users' activity (that is what
they are doing). Traditionally any context sensing was conducted with hardware
sensors. However, software can also play the same role and in some situations
will be more useful to sense the activity of the user. Furthermore they can
make use of the fact that Service-oriented systems exchange information through
standard protocols. In this paper we discuss our proposed approach to sense the
activity of the user making use of software
Signatures of a magnetic-field-induced Lifshitz transition in the ultra-quantum limit of the topological semimetal ZrTe5
The quantum limit (QL) of an electron liquid, realised at strong magnetic fields, has long been proposed to host a wealth of strongly correlated states of matter. Electronic states in the QL are, for example, quasi-one dimensional (1D), which implies perfectly nested Fermi surfaces prone to instabilities. Whereas the QL typically requires unreachably strong magnetic fields, the topological semimetal ZrTe5 has been shown to reach the QL at fields of only a few Tesla. Here, we characterize the QL of ZrTe5 at fields up to 64 T by a combination of electrical-transport and ultrasound measurements. We find that the Zeeman effect in ZrTe5 enables an efficient tuning of the 1D Landau band structure with magnetic field. This results in a Lifshitz transition to a 1D Weyl regime in which perfect charge neutrality can be achieved. Since no instability-driven phase transitions destabilise the 1D electron liquid for the investigated field strengths and temperatures, our analysis establishes ZrTe5 as a thoroughly understood platform for potentially inducing more exotic interaction-driven phases at lower temperatures
Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance
We report detailed 17O, 139La, and 63Cu Nuclear Magnetic Resonance (NMR) and
Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered
La1.875Ba0.125CuO4 single crystal and in oriented powder samples of
La1.8-xEu0.2SrxCuO4. We observe a partial wipeout of the 17O NMR intensity and
a simultaneous drop of the 17O electric field gradient (EFG) at low
temperatures where the spin stripe order sets in. In contrast, the 63Cu
intensity is completely wiped out at the same temperature. The drop of the 17O
quadrupole frequency is compatible with a charge stripe order. The 17O spin
lattice relaxation rate shows a peak similar to that of the 139La, which is of
magnetic origin. This peak is doping dependent and is maximal at x ~ 1/8.Comment: submitted to European Physical Journal Special Topic
History and Applications of Dust Devil Studies
Studies of dust devils, and their impact on society, are reviewed. Dust devils have been noted since antiquity, and have been documented in many countries, as well as on the planet Mars. As time-variable vortex entities, they have become a cultural motif. Three major stimuli of dust devil research are identified, nuclear testing, terrestrial climate studies, and perhaps most significantly, Mars research. Dust devils present an occasional safety hazard to light structures and have caused several deaths
Cohort profile: Zoe 2.0—a community-based genetic epidemiologic study of early childhood oral health
Early childhood caries (ECC) is an aggressive form of dental caries occurring in the first five years of life. Despite its prevalence and consequences, little progress has been made in its prevention and even less is known about individuals’ susceptibility or genomic risk factors. The genome-wide association study (GWAS) of ECC (“ZOE 2.0”) is a community-based, multi-ethnic, cross-sectional, genetic epidemiologic study seeking to address this knowledge gap. This paper describes the study’s design, the cohort’s demographic profile, data domains, and key oral health outcomes. Between 2016 and 2019, the study enrolled 8059 3–5-year-old children attending public preschools in North Carolina, United States. Participants resided in 86 of the state’s 100 counties and racial/ethnic minorities predominated—for example, 48% (n = 3872) were African American, 22% white, and 20% (n = 1611) were Hispanic/Latino. Seventy-nine percent (n = 6404) of participants underwent clinical dental examinations yielding ECC outcome measures—ECC (defined at the established caries lesion threshold) prevalence was 54% and the mean number of decayed, missing, filled surfaces due to caries was eight. Nearly all (98%) examined children provided sufficient DNA from saliva for genotyping. The cohort’s community-based nature and rich data offer excellent opportunities for addressing important clinical, epidemiologic, and biological questions in early childhood
Dynamic electron correlations with charge order wavelength along all directions in the copper oxide plane
In strongly correlated systems the strength of Coulomb interactions between
electrons, relative to their kinetic energy, plays a central role in
determining their emergent quantum mechanical phases. We perform resonant x-ray
scattering on BiSrCaCuO, a prototypical cuprate
superconductor, to probe electronic correlations within the CuO plane. We
discover a dynamic quasi-circular pattern in the - scattering plane with
a radius that matches the wave vector magnitude of the well-known static charge
order. Along with doping- and temperature-dependent measurements, our
experiments reveal a picture of charge order competing with superconductivity
where short-range domains along and can dynamically rotate into any
other in-plane direction. This quasi-circular spectrum, a hallmark of
Brazovskii-type fluctuations, has immediate consequences to our understanding
of rotational and translational symmetry breaking in the cuprates. We discuss
how the combination of short- and long-range Coulomb interactions results in an
effective non-monotonic potential that may determine the quasi-circular
pattern.Comment: This is a post-peer-review, pre-copyedit version of an article
published in Nature Communications. The final authenticated version is
available online at: https://doi.org/10.1038/s41467-020-20824-7.
Supplementary materials are available through the published version in Nature
Communication
Measurement of the Lambda^0_b lifetime in the decay Lambda^0_b -> J/psi Lambda^0 with the D0 Detector
We present measurements of the Lambda^0_b lifetime in the exclusive decay
channel Lambda^0_{b}->J/psi Lambda^0, with J/psi to mu+ mu- and Lambda^0 to p
pi-, the B^0 lifetime in the decay B^0 -> J/psi K^0_S with J/psi to mu+ mu- and
K^0_S to pi+ pi-, and the ratio of these lifetimes. The analysis is based on
approximately 250 pb^{-1} of data recorded with the D0 detector in pp(bar)
collisions at sqrt{s}=1.96 TeV. The Lambda^0_b lifetime is determined to be
tau(Lambda^0_b) = 1.22 +0.22/-0.18 (stat) +/- 0.04 (syst) ps, the B^0 lifetime
tau(B^0) = 1.40 +0.11/-0.10 (stat) +/- 0.03 (syst) ps, and the ratio
tau(Lambda^0_b)/tau(B^0) = 0.87 +0.17/-0.14 (stat) +/- 0.03 (syst). In contrast
with previous measurements using semileptonic decays, this is the first
determination of the Lambda^0_b lifetime based on a fully reconstructed decay
channel.Comment: 7 pages, 4 figures, Submitted to Physical Review Letters, v2: Added
FNAL Pub-numbe
New insights into the genetic etiology of Alzheimer's disease and related dementias
Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele
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