275 research outputs found
Filling the Void: A Low Cost, High-Yield Method to Addressing Incidental Findings in Trauma Patients
In this study we:
Report the incidence of incidental findings in a suburban trauma center treating primarily blunt and elderly trauma
Propose simple solutions to increase the rate of disclosure to patientshttps://jdc.jefferson.edu/patientsafetyposters/1070/thumbnail.jp
Studies of superconducting materials with muon spin rotation
The muon spin rotation/relaxation technique was found to be an exceptionally effective means of measuring the magnetic properties of superconductors, including the new high temperature superconductor materials, at the microscopic level. The technique directly measures the magnetic penetration depth (type II superconductors (SC's)) and detects the presence of magnetic ordering (antiferromagnetism or spin-glass ordering were observed in some high temperature superconductor (HTSC's) and in many closely related compounds). Extensive studies of HTSC materials were conducted by the Virginia State University - College of William and Mary - Columbia University collaboration at Brookhaven National Laboratory and TRIUMF (Vancouver). A survey of LaSrCuO and YBaCaCuO systems shows an essentially linear relationship between the transition temperature T(sub c) and the relaxation rate. This appears to be a manifestation of the proportionality between T(sub c) and the Fermi energy, which suggests a high energy scale for the SC coupling, and which is not consistent with the weak coupling of phonon-mediated SC. Studies of LaCuO and YBaCuO parent compounds show clear evidence of antiferromagnetism. YBa2Cu(3-x)CO(x)O7 shows the simultaneous presence of spin-glass magnetic ordering and superconductivity. Three-dimensional SC, (Ba, K) BiO3, unlike the layered CuO-based compounds, shows no suggestion of magnetic ordering. Experimental techniques and theoretical implications are discussed
Anomalous Spin Dynamics in Doped Quantum Antiferromagnets
Finite-temperature spin dynamics in planar t-J model is studied using the
method based on the Lanczos diagonalization of small systems. Dynamical spin
structure factor at moderate dopings shows the coexistence of free-fermion-like
and spin-fluctuation timescales. At T<J, the low-frequency and static
susceptibility show pronounced T dependence, supporting a scenario, related to
the marginal Fermi-liquid one, for the explanation of neutron-scattering and
NMR-relaxation experiments in cuprates. Calculated NMR relaxation rates
reasonably reproduce experimental ones.Comment: 10 pages + 4 figures, Postscript in uuencoded compressed tar file,
IJS-TP-94/2
Antiferromagnetic Excitations and Van Hove Singularities in YBaCuO
We show that in quasi-two-dimensional -wave superconductors Van Hove
singularities close to the Fermi surface lead to novel magnetic quasi-particle
excitations. We calculate the temperature and doping dependence of dynamical
magnetic susceptibility for YBCO and show that the proposed excitations are in
agreement with inelastic neutron scattering experiments. In addition, the
values of the gap parameter and in-plane antiferromagnetic coupling are much
smaller than usually believed.Comment: REVTeX, 4 pages + 3 PostScript (compressed) figures; to appear in
Phys. Rev. B (Rap. Comm.
On the Magnetic Excitation Spectra of High Tc Cu Oxides up to the Energies far above the Resonance Energy
Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy and La214 systems have been
studied. For La1.88Sr0.12CuO4, c"(q,w) have been measured up to ~30 meV and
existing data have been analyzed up to the energy w~150 meV by using the
phenomenological expression of the generalized magnetic susceptibility
c(q,w)=c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is the susceptibility of the
electrons without the exchange coupling J(q) among them. In the relatively low
energy region up to slightly above the resonance energy Er, it has been
reported by the authors' group that the expression can explain characteristics
of the q- and w-dependence of the spectra of YBa2Cu3Oy (YBCO or YBCOy). Here,
it is also pointed out that the expression can reproduce the rotation of four
incommensurate peaks of c"(q,w) within the a*-b* plane about (p/a, p/a) {or
so-called (p, p)} point by 45 degree, which occurs as w goes to the energy
region far above Er from E below Er. For La2-xSrxCuO4 and La2-xBaxCuO4,
agreements between the observed results and the calculations are less
satisfactory than for YBCO, indicating that we have to take account of the
existence of the "stripes" to consistently explain the observed c"(q,w) of
La214 system especially near x=1/8.Comment: 14 pages, 5 figure
Herbivore-mediated negative frequency-dependent selection underlies a trichome dimorphism in nature
Authors are grateful for funding provided by an NSF GRFP to J.K.G. (2015195769) and DEB‐1353970 to L.F.D.Negative frequency‐dependent selection (NFDS) has been shown to maintain polymorphism in a diverse array of traits. The action of NFDS has been confirmed through modeling, experimental approaches, and genetic analyses. In this study, we investigated NFDS in the wild using morph‐frequency changes spanning a 20‐year period from over 30 dimorphic populations of Datura wrightii. In these populations, plants either possess glandular (sticky) or non‐glandular (velvety) trichomes, and the ratio of these morphs varies substantially among populations. Our method provided evidence that NFDS, rather than drift or migration, is the primary force maintaining this dimorphism. Most populations that were initially dimorphic remained dimorphic, and the overall mean and variance in morph frequency did not change over time. Furthermore, morph‐frequency differences were not related to geographic distances. Together, these results indicate that neither directional selection, drift, or migration played a substantial role in determining morph frequencies. However, as predicted by negative frequency‐dependent selection, we found that the rare morph tended to increase in frequency, leading to a negative relationship between the change in the frequency of the sticky morph and its initial frequency. In addition, we found that morph‐frequency change over time was significantly correlated with the damage inflicted by two herbivores: Lema daturaphila and Tupiochoris notatus. The latter is a specialist on the sticky morph and damage by this herbivore was greatest when the sticky morph was common. The reverse was true for L. daturaphila, such that damage increased with the frequency of the velvety morph. These findings suggest that these herbivores contribute to balancing selection on the observed trichome dimorphism.Publisher PDFPeer reviewe
Freezing of anisotropic spin clusters in La1.98Sr0.02CuO4
A spin-glass compound, LaSrCuO, shows
quasi-three-dimensional magnetic ordering below 40 K. A remarkable
feature is that the magnetic correlation length along the orthorhombic
axis is much longer than that along the axis,
suggesting that the spin structure is closely related to the diagonal stripe
structure. The spin-glass state can be expressed as a random freezing of
quasi-three-dimensional spin clusters with anisotropic spin correlations
( \AA, \AA, and \AA at 1.6 K).
The new magnetic state is important as an intermediate phase between the
three-dimensional antiferromagnetic ordered phase in LaCuO and the
incommensurate phase in LaSrCuO in which the positions of
the incommensurate peaks are rotated by 45 in reciprocal space about
(,) from those observed in the superconducting LaCuO
compounds.Comment: 7 pages, RevTex, 8 PS figures, submitted to Phys. Rev.
Pseudogap Induced Antiferromagnetic Spin Correlation in High-Temperature Superconductors
The pseudogap phenomena observed on cuprate high temperature superconductors
are investigated based on the exact diagonalization method on the finite
cluster t-J model. The results show the presence of the gap-like behavior in
the temperature dependence of various magnetic properties; the NMR relaxation
rate, the neutron scattering intensity and the static susceptibility. The
calculated spin correlation function indicates that the pseudogap behavior
arises associated with the development of the antiferromagnetic spin
correlation with decreasing the temperature. The numerical results are
presented to clarify the model parameter dependence, that covers the realistic
experimental situation. The effect of the next-nearest neighbor hopping is
also studied.Comment: 7 pages, Revtex, with 10 eps figures, to appear in J. Phys. Soc. Jpn.
(Vol. 70, No. 1
Charge Segregation, Cluster Spin-Glass and Superconductivity in La1.94Sr0.06CuO4
A 63Cu and 139La NMR/NQR study of superconducting (Tc=7 K) La1.94Sr0.06CuO4
single crystal is reported. Coexistence of spin-glass and superconducting
phases is found below ~5 K from 139La NMR relaxation. 63Cu and 139La NMR
spectra show that, upon cooling, CuO2 planes progressively separate into two
magnetic phases, one of them having enhanced antiferromagnetic correlations.
These results establish the AF-cluster nature of the spin-glass. We discuss how
this phase can be related to the microsegregation of mobile holes and to the
possible pinning of charge-stripes.Comment: 4 pages. Modified manuscript with clarification
Essential Role of the Cooperative Lattice Distortion in the Charge, Orbital and Spin Ordering in doped Manganites
The role of lattice distortion in the charge, orbital and spin ordering in
half doped manganites has been investigated. For fixed magnetic ordering, we
show that the cooperative lattice distortion stabilize the experimentally
observed ordering even when the strong on-site electronic correlation is taken
into account. Furthermore, without invoking the magnetic interactions, the
cooperative lattice distortion alone may lead to the correct charge and orbital
ordering including the charge stacking effect, and the magnetic ordering can be
the consequence of such a charge and orbital ordering. We propose that the
cooperative nature of the lattice distortion is essential to understand the
complicated charge, orbital and spin ordering observed in doped manganites.Comment: 5 pages,4 figure
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