1,266 research outputs found
Broadening of Andreev-Bound States in d_{x^2-y^2} superconductors
We investigate the broadening of the bound states at an interface of an
unconventional superconductor by bulk impurity scattering. We use the
quasiclassical theory and include impurity scattering in the Born and in the
unitarity limit. The broadening of bound states due to unitary scatterers is
shown to be substantially weaker than in the Born limit. We study various model
geometries and calculate the temperature dependence of the Josephson critical
current in the presence of these impurity-broadened bound states.Comment: 6 page including 7 figures, submitted to Phys. Rev.
Van der Waals density functional: Self-consistent potential and the nature of the van der Waals bond
We derive the exchange-correlation potential corresponding to the nonlocal
van der Waals density functional [M. Dion, H. Rydberg, E. Schroder, D. C.
Langreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004)]. We use this
potential for a self-consistent calculation of the ground state properties of a
number of van der Waals complexes as well as crystalline silicon. For the
latter, where little or no van der Waals interaction is expected, we find that
the results are mostly determined by semilocal exchange and correlation as in
standard generalized gradient approximations (GGA), with the fully nonlocal
term giving little effect. On the other hand, our results for the van der Waals
complexes show that the self-consistency has little effect at equilibrium
separations. This finding validates previous calculations with the same
functional that treated the fully nonlocal term as a post GGA perturbation. A
comparison of our results with wave-function calculations demonstrates the
usefulness of our approach. The exchange-correlation potential also allows us
to calculate Hellmann-Feynman forces, hence providing the means for efficient
geometry relaxations as well as unleashing the potential use of other standard
techniques that depend on the self-consistent charge distribution. The nature
of the van der Waals bond is discussed in terms of the self-consistent bonding
charge.Comment: submitted to Phys. Rev.
Quasiparticle Interface States in Junctions Involving d-Wave Superconductors
Influence of surface pair breaking, barrier transmission and phase difference
on quasiparticle bound states in junctions with d-wave superconductors is
examined. Based on the quasiclassical theory of superconductivity, an approach
is developed to handle interface bound states. It is shown in SIS' junctions
that low energy bound states get their energies reduced by surface pair
breaking, which can be taken into account by introducing an effective order
parameter for each superconductor at the junction barrier. More interestingly,
for the interface bound states near the continuous spectrum the effect of
surface pair breaking may result in a splitting of the bound states. In the
tunneling limit this can lead to a square root dependence of a nonequilibrium
Josephson current on the barrier transmision, which means an enhancement as
compared to the conventional critical current linear in the transmission.
Reduced broadening of bound states in NIS junctions due to surface pair
breaking is found.Comment: 27 pages, Latex fil
Inventing Maternity: Politics, Science, and Literature, 1650-1865
Not until the eighteenth century was the image of the tender, full-time mother invented. This image retains its power today. Inventing Maternity demonstrates that, despite its association with an increasingly standardized set of values, motherhood remained contested terrain. Drawing on feminist, cultural, and postcolonial theory, Inventing Maternity surveys a wide range of sources--medical texts, political tracts, religious doctrine, poems, novels, slave narratives, conduct books, and cookbooks. The first half of the volume, covering the mid-seventeenth to the late eighteenth centuries, considers central debates about fetal development, pregnancy, breastfeeding, and childbearing. The second half, covering the late eighteenth to the mid-nineteenth centuries, charts a historical shift to the regulation of reproduction as maternity is increasingly associated with infanticide, population control, poverty, and colonial, national, and racial instability. In her introduction, Greenfield provides a historical overview of early modern interpretations of maternity. She concludes with a consideration of their impact on current debates about reproductive rights and technologies, child custody, and the cycles of poverty.
Honorable Mention for collaborative work from the Society for Early Modern Women
Susan C. Greenfield is associate professor of English at Fordham University. Carol Barash is the author of English Women\u27s Poetry, 1649-1714 and co-editor of Major Women Writers of Seventeenth-Century England.
These essays offer fresh and vigorous arguments for the challenges maternal roles present to social values. —Choice
It is extremely difficult to capture and convey the complex richness of this volume. Taken together, the constitutive essays offer a historical analysis of the making of modern maternity that is sure to appeal to a wide variety of readers. —Journal of the Association for Research on Mothering
Makes a timely and valuable contribution to the current scholarly conversation concerning maternity, reproduction, and the gendered body in which histories of imaginative narrative are profitably understood in conjunction with theories of gender, sexuality, race, and class. —Julia Sternhttps://uknowledge.uky.edu/upk_gender_and_sexuality_studies/1005/thumbnail.jp
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Giardia Colonizes and Encysts in High-Density Foci in the Murine Small Intestine.
Giardia lamblia is a highly prevalent yet understudied protistan parasite causing significant diarrheal disease worldwide. Hosts ingest Giardia cysts from contaminated sources. In the gastrointestinal tract, cysts excyst to become motile trophozoites, colonizing and attaching to the gut epithelium. Trophozoites later differentiate into infectious cysts that are excreted and contaminate the environment. Due to the limited accessibility of the gut, the temporospatial dynamics of giardiasis in the host are largely inferred from laboratory culture and thus may not mirror Giardia physiology in the host. Here, we have developed bioluminescent imaging (BLI) to directly interrogate and quantify the in vivo temporospatial dynamics of Giardia infection, thereby providing an improved murine model to evaluate anti-Giardia drugs. Using BLI, we determined that parasites primarily colonize the proximal small intestine nonuniformly in high-density foci. By imaging encystation-specific bioreporters, we show that encystation initiates shortly after inoculation and continues throughout the duration of infection. Encystation also initiates in high-density foci in the proximal small intestine, and high density contributes to the initiation of encystation in laboratory culture. We suggest that these high-density in vivo foci of colonizing and encysting Giardia likely result in localized disruption to the epithelium. This more accurate visualization of giardiasis redefines the dynamics of the in vivo Giardia life cycle, paving the way for future mechanistic studies of density-dependent parasitic processes in the host. IMPORTANCEGiardia is a single-celled parasite causing significant diarrheal disease in several hundred million people worldwide. Due to limited access to the site of infection in the gastrointestinal tract, our understanding of the dynamics of Giardia infections in the host has remained limited and largely inferred from laboratory culture. To better understand Giardia physiology and colonization in the host, we developed imaging methods to quantify Giardia expressing bioluminescent physiological reporters in two relevant animal models. We discovered that parasites primarily colonize and encyst in the proximal small intestine in discrete, high-density foci. We also show that high parasite density contributes to encystation initiation
Subharmonic Gap Structure in Superconductor/Ferromagnet/Superconductor Junctions
The behavior of dc subgap current in magnetic quantum point contact is
discussed for the case of low-transparency junction with different tunnel
probabilities for spin-up () and spin-down ()
electrons. Due to the presence of Andreev bound states in the
system the positions of subgap electric current steps are split at temperature with respect to the
nonmagnetic result . It is found that under the condition
the spin current also manifests subgap
structure, but only for odd values of . The split steps corresponding to
in subgap electric and spin currents are analytically calculated and
the following steps are described qualitatively.Comment: 4 pages, 1 figure, minor stylistic changes, journal-ref adde
Combined Paramagnetic and Diamagnetic Response of YBCO
It has been predicted that the zero frequency density of states of YBCO in
the superconducting phase can display interesting anisotropy effects when a
magnetic field is applied parallel to the copper-oxide planes, due to the
diamagnetic response of the quasi-particles. In this paper we incorporate
paramagnetism into the theory and show that it lessens the anisotropy and can
even eliminate it altogether. At the same time paramagnetism also changes the
scaling with the square root of the magnetic field first deduced by Volovik
leading to an experimentally testable prediction. We also map out the analytic
structure of the zero frequency density of states as a function of the
diamagnetic and paramagnetic energies. At certain critical magnetic field
values we predict kinks as we vary the magnetic field. However these probably
lie beyond currently accessible field strengths
Casimir torque
We develop a formalism for the calculation of the flow of angular momentum
carried by the fluctuating electromagnetic field within a cavity bounded by two
flat anisotropic materials. By generalizing a procedure employed recently for
the calculation of the Casimir force between arbitrary materials, we obtain an
expression for the torque between anisotropic plates in terms of their
reflection amplitude matrices. We evaluate the torque in 1D for ideal and
realistic model materials.Comment: 8 pages, 4 figs, Submitted to Proc. of QFEXT'05, to appear in J.
Phys.
A General Approach to Casimir Force Problems Based on Local Reflection Amplitudes and Huygen's Principle
In this paper we describe an approach to Casimir Force problems that is
ultimately generalizable to all fields, boundary conditions, and cavity
geometries. This approach utilizes locally defined reflection amplitudes to
express the energy per unit area of any Casimir interaction. To demonstrate
this approach we solve a number of Casimir Force problems including the case of
uniaxial boundary conditions in a parallel-plate cavity.Comment: 9 pages, 5 figures, Equation 18 has been corrected, [v1] contained a
typ
Spectral representation of the Casimir Force Between a Sphere and a Substrate
We calculate the Casimir force in the non-retarded limit between a spherical
nanoparticle and a substrate, and we found that high-multipolar contributions
are very important when the sphere is very close to the substrate. We show that
the highly inhomegenous electromagnetic field induced by the presence of the
substrate, can enhance the Casimir force by orders of magnitude, compared with
the classical dipolar approximation.Comment: 5 page + 4 figures. Submitted to Phys. Rev. Let
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