1,156 research outputs found
Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15
The normal-state in-plane resistivity below the zero-field superconducting
transition temperature and the upper critical field Hc2 were measured by
suppressing superconductivity in pulsed magnetic fields for
K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity is found to
increase logarithmically with decrasing temperature as
. Similar to granular metals, our results suggest
that a superconductor - insulator transition below zero-field T may be
induced in high magnetic fields. This is related to the intrinsic real-space
phase-separated states common to all inhomogeneous superconductors.Comment: 6 pages, 4 figure
Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet CsCuBr
We report on high-field electron spin resonance (ESR) studies of magnetic
excitations in the spin-1/2 triangular-lattice antiferromagnet CsCuBr.
Frequency-field diagrams of ESR excitations are measured for different
orientations of magnetic fields up to 25 T. We show that the substantial
zero-field energy gap, K, observed in the low-temperature
excitation spectrum of CsCuBr [Zvyagin , Phys. Rev. Lett. 112,
077206 (2014)], is present well above . Noticeably, the transition into
the long-range magnetically ordered phase does not significantly affect the
size of the gap, suggesting that even below the high-energy spin dynamics
in CsCuBr is determined by short-range-order spin correlations. The
experimental data are compared with results of model spin-wave-theory
calculations for spin-1/2 triangle-lattice antiferromagnet.Comment: 6 pages, 9 figure
Amyloid positron emission tomography candidates may focus more on benefits than risks of results disclosure
IntroductionGiven mounting calls to disclose biomarker test results to research participants, we explored factors underlying decisions by patients with mild cognitive impairment to receive amyloid imaging results.MethodsProspective, qualitative interviews were conducted with 59 participants (30 = mild cognitive impairment patients, 29 = care partners) from the scan arm of a randomized controlled trial on the effects of amyloid PET results disclosure in an Alzheimer Disease Research Center setting.ResultsSixty‐three percent of the participants were female, with an average age of 72.9 years, and most had greater than a high school level of education (80%). Primary motivations included: (1) better understanding one’s mild cognitive impairment etiology and prognosis to plan ahead, and (2) learning one’s brain amyloid status for knowledge’s sake, regardless of whether the information is actionable. Most participants demonstrated an adequate understanding of the scan’s limitations, yet instances of characterizing amyloid PET as a definitive test for Alzheimer’s disease occurred. Mention of potential drawbacks, such as negative psychological outcomes, was minimal, even among care partners.DiscussionFindings demonstrate a risk of disproportionate focus on possible benefits of testing among amyloid scan candidates and suggest a need to clearly emphasize the limitations of amyloid PET when counseling cognitively impaired patients and their families before testing. Future research should examine whether minimizing drawbacks at the pre‐imaging stage has adverse consequences on results disclosure.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152635/1/dad2jdadm201805003.pd
Perturbation of the Hematopoietic System during Embryonic Liver Development Due to Disruption of Polyubiquitin Gene Ubc in Mice
Disruption of the polyubiquitin gene Ubc leads to a defect in fetal liver development, which can be partially rescued by increasing the amount of ubiquitin. However, it is still not known why Ubc is required for fetal liver development and the nature of the defective cell types responsible for embryonic lethality have not been characterized. In this study, we assessed the cause of embryonic lethality with respect to the fetal liver hematopoietic system. We found that Ubc was highly expressed in the embryonic liver, and the proliferation capacity of fetal liver cells was reduced in Ubc−/− embryos. Specifically, Ubc was most highly expressed in hematopoietic cells, and the proliferation capacity of hematopoietic cells was significantly impaired in Ubc−/− embryos. While hematopoietic cell and hematopoietic stem cell (HSC) frequency was maintained in Ubc−/− embryos, the absolute number of these cells was diminished because of reduced total liver cell number in Ubc−/− embryos. Transplantations of fetal liver cells into lethally irradiated recipient mice by non-competitive and competitive reconstitution methods indicated that disruption of Ubc does not significantly impair the intrinsic function of fetal liver HSCs. These findings suggest that disruption of Ubc reduces the absolute number of HSCs in embryonic livers, but has no significant effect on the autonomous function of HSCs. Thus, the lethality of Ubc−/− embryos is not the result of intrinsic HSC failure
Local structural disorder and superconductivity in KxFe2-ySe2
We report significantly enhanced magnetic moment in
K0.69(2)Fe1.45(1)Se2.00(1) single crystals with sharp Tc and bulk
superconductivity obtained by postannealing and quenching process. There are
two Fe sites in the K0.69(2)Fe1.45(1)Se2.00(1) unit cell: Fe1, which has higher
symmetry with longer average Fe-Se bond length, and Fe2, which has lower
symmetry with shorter average Fe-Se bond length. Temperature-dependent x-ray
absorption fine-structure (XAFS) analysis results on quenched and as-grown
K0.69(2)Fe1.45(1)Se2.00(1) crystals show that quenched
K0.69(2)Fe1.45(1)Se2.00(1) have increased average Fe-Se bond length and
decreased static disorder. Our results indicate that nonzero population of Fe1
sites is the key structural parameter that governs the bulk superconductivity.
We also show clear evidence that Fe1 sites carry higher magnetic moment than
Fe2 sites.Comment: 3 figures, 4 page
The Price of Anarchy in Transportation Networks: Efficiency and Optimality Control
Uncoordinated individuals in human society pursuing their personally optimal
strategies do not always achieve the social optimum, the most beneficial state
to the society as a whole. Instead, strategies form Nash equilibria which are
often socially suboptimal. Society, therefore, has to pay a price of anarchy
for the lack of coordination among its members. Here we assess this price of
anarchy by analyzing the travel times in road networks of several major cities.
Our simulation shows that uncoordinated drivers possibly waste a considerable
amount of their travel time. Counterintuitively,simply blocking certain streets
can partially improve the traffic conditions. We analyze various complex
networks and discuss the possibility of similar paradoxes in physics.Comment: major revisions with multicommodity; Phys. Rev. Lett., accepte
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