1,963 research outputs found
Interaction of artemisinin and tetracycline or erythromycin against Plasmodium falciparum in vitro
Antimalarial activities of tetracycline (TC) and erythromycin (EM), alone or in combination with artemisinin (Qinghaosu, QHS), were studied using chloroquine (CQ)-sensitive (D6) and -resistant (W2) strains of Plasmodium falciparum in vitro. The antimalarial potency of TC (IC50 = 9862 nM for the CQ-sensitive parasite, 32414 nM for the CQ-resistant one) or EM (IC50 = 45787 nM for the CQ-sensitive parasite, 33397 nM for the CQ-resistant one) was much less than that of QHS (IC50 ranging from 25 to 40 nM). The CQ-resistant falciparum parasite displayed a cross-resistance to TC, while both the drug-sensitive and -resistant parasites exhibited similar responses to EM. However, antimalarial potency of EM appeared to be less than that of TC against the drug-sensitive parasite. When TC was combined with QHS, an additive interaction was observed against the CQ-sensitive falciparum parasite, while synergism was found with the CQ-resistant parasite. When EM was tested in combination with QHS, a potentiating interaction occurred with both the CQ-sensitive and -resistant falciparum parasite. The above results indicated that the QHS combination with either TC or EM may be a promising antimalarial preparation with low recrudescence compared to artemisinin used alone in clinical practice
Discovery of an OVI Emitting Nebula around the Hot White Dwarf KPD 0005+5106
A survey of diffuse interstellar sight lines observed with the Far
Ultraviolet Spectroscopic Explorer has led to the serendipitous discovery of a
high-ionization nebula around the hot white dwarf KPD 0005+5106. The nebula has
an OVI 1032A surface brightness of up to 25,000 photons/s/cm^2/sr, making it
the brightest region of extended OVI emission in our survey. Photoionization
models using the incident white dwarf continuum successfully reproduce the
observed OVI intensity. The OVI emission arises in the highly ionized inner
region of a planetary nebula around KPD 0005+5106. This newly discovered nebula
may be one member of a class of high-ionization planetary nebulae that are
difficult to detect in the optical, but which can be easily identified in the
ultraviolet.Comment: accepted for publication in ApJL, 11 pages including 2 figure
Direct Evidence for a Magnetic f-electron Mediated Cooper Pairing Mechanism of Heavy Fermion Superconductivity in CeCoIn5
To identify the microscopic mechanism of heavy-fermion Cooper pairing is an
unresolved challenge in quantum matter studies; it may also relate closely to
finding the pairing mechanism of high temperature superconductivity.
Magnetically mediated Cooper pairing has long been the conjectured basis of
heavy-fermion superconductivity but no direct verification of this hypothesis
was achievable. Here, we use a novel approach based on precision measurements
of the heavy-fermion band structure using quasiparticle interference (QPI)
imaging, to reveal quantitatively the momentum-space (k-space) structure of the
f-electron magnetic interactions of CeCoIn5. Then, by solving the
superconducting gap equations on the two heavy-fermion bands
with these magnetic interactions as mediators of the
Cooper pairing, we derive a series of quantitative predictions about the
superconductive state. The agreement found between these diverse predictions
and the measured characteristics of superconducting CeCoIn5, then provides
direct evidence that the heavy-fermion Cooper pairing is indeed mediated by the
f-electron magnetism.Comment: 19 pages, 4 figures, Supplementary Information: 31 pages, 5 figure
Promoting Transformative Learning: Extension Partnerships Focused on an Ethic of Caring
Extension is known for creating educational environments conducive to the transformative learning required for people to change their perspectives and make better decisions in their lives. However, creating such environments is not easy. The complex Extension context often produces barriers to including program components that support transformative learning. Extension partnerships with nonprofits, government units, and businesses can reduce these barriers and enhance the potential for transformative learning by fostering caring program environments. A partnership between Extension and United Way exemplifies one model for developing programs focused on creating caring educational environments that encourage and sustain transformative learning
The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5
We report observations of the hot post-asymptotic giant branch star ZNG 1 in
the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic
Explorer (FUSE). From the resulting spectrum, we derive an effective
temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a
rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) =
3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon
(2.6% by mass), nitrogen (0.51%) and oxygen (0.37%) abundances. The spectrum
shows evidence for a wind with terminal velocity near 1000 km/s and an
expanding shell of carbon- and nitrogen-rich material around the star. The
abundance pattern of ZNG 1 is suggestive of the ``born-again'' scenario,
whereby a star on the white-dwarf cooling curve undergoes a very late shell
flash and returns to the AGB, but the star's rapid rotation is more easily
explained by a previous interaction with a binary companion.Comment: 8 pages, 2 PostScript figures, Latex with emulateapj5. Accepted for
publication in ApJ Letter
Motion of vortices in type II superconductors
The methods of formal asymptotics are used to examine the behaviour of a system of curvilinear vortices in a type II superconductor as the thickness of the vortex cores tends to zero. The vortices then appear as singularities in the field equation and are analagous to line vortices in inviscid hydrodynamics. A local analysis near each vortex core gives an equation of motion governing the evolution of these singularities
A note on leapfrogging vortex rings
In this paper we provide examples, by numerical simulation using the Navier-Stokes equations for axisymmetric laminar flow, of the 'leapfrogging' motion of two, initially identical, vortex rings which share a common axis of symmetry. We show that the number of clear passes that each ring makes through the other increases with Reynolds number, and that as long as the configuration remains stable the two rings ultimately merge to form a single vortex ring
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