1,721 research outputs found
The Structure of a Vortex in the t-J Model
We study the single-vortex solution of the t-J model within
resonating-valence-bond (RVB) mean-field theory. We find two types of vortex
cores, insulating and metallic, depending on the parameters of the model. The
pairing order parameter near both cores have
symmetry. For some range of the calculated tunneling spectrum of the
metallic vortex core agrees qualitatively with the STM tunneling data for
BSCCO
Universality in the Screening Cloud of Dislocations Surrounding a Disclination
A detailed analytical and numerical analysis for the dislocation cloud
surrounding a disclination is presented. The analytical results show that the
combined system behaves as a single disclination with an effective fractional
charge which can be computed from the properties of the grain boundaries
forming the dislocation cloud. Expressions are also given when the crystal is
subjected to an external two-dimensional pressure. The analytical results are
generalized to a scaling form for the energy which up to core energies is given
by the Young modulus of the crystal times a universal function. The accuracy of
the universality hypothesis is numerically checked to high accuracy. The
numerical approach, based on a generalization from previous work by S. Seung
and D.R. Nelson ({\em Phys. Rev A 38:1005 (1988)}), is interesting on its own
and allows to compute the energy for an {\em arbitrary} distribution of
defects, on an {\em arbitrary geometry} with an arbitrary elastic {\em energy}
with very minor additional computational effort. Some implications for recent
experimental, computational and theoretical work are also discussed.Comment: 35 pages, 21 eps file
UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group
We present UBVI surface photometry for 20.'5 X 20.'5 area of a late-type
spiral galaxy NGC 300. In order to understand the morphological properties and
luminosity distribution characteristics of NGC 300, we have derived isophotal
maps, surface brightness profiles, ellipticity profiles, position angle
profiles, and color profiles. By merging the I-band data of our surface
brightness measurements with those of Boeker et al. (2002) based on Hubble
Space Telescope observations, we have made combined I-band surface brightness
profiles for the region of 0."02 < r < 500" and decomposed the profiles into
three components: a nucleus, a bulge, and an exponential disk.Comment: 16 pages(cjaa209.sty), Accepted by the Chinese J. Astron. Astrophys.,
Fig 2 and 8 are degraded to reduce spac
Insights into Hunter syndrome from the structure of iduronate-2-sulfatase
Hunter syndrome is a rare but devastating childhood disease caused by mutations in the IDS gene encoding iduronate-2-sulfatase, a crucial enzyme in the lysosomal degradation pathway of dermatan sulfate and heparan sulfate. These complex glycosaminoglycans have important roles in cell adhesion, growth, proliferation and repair, and their degradation and recycling in the lysosome is essential for cellular maintenance. A variety of disease-causing mutations have been identified throughout the IDS gene. However, understanding the molecular basis of the disease has been impaired by the lack of structural data. Here, we present the crystal structure of human IDS with a covalently bound sulfate ion in the active site. This structure provides essential insight into multiple mechanisms by which pathogenic mutations interfere with enzyme function, and a compelling explanation for severe Hunter syndrome phenotypes. Understanding the structural consequences of disease-associated mutations will facilitate the identification of patients that may benefit from specific tailored therapies.We acknowledge Diamond Light Source for time on beamline I03 under proposal MX6641. We thank Shire Pharmaceuticals for providing Elaprase (idursulfase) and Tom Terwilliger for helpful advice on multi-crystal averaging. We also thank Alexandre Bonvin for modifying HADDOCK to support the non-standard amino acid FGH (PDB code DDZ). R.J.R. is supported by a Principal Research Fellowship funded by the Wellcome Trust (Grant 082961/Z/07/Z), which also supported C.H.H. and M.D. A.Z. was supported by a Senior Research Fellowship from the British Heart Foundation (PG/09/072/27945). J.E.D. is supported by a Royal Society University Research Fellowship (UF100371). Support received from the US National Institutes of Health (grant P01GM063210 R.J.R.) is gratefully acknowledged. The research was facilitated by a Wellcome Trust Strategic Award (100140) to the Cambridge Institute for Medical Research
Quantum magnetism and criticality
Magnetic insulators have proved to be fertile ground for studying new types
of quantum many body states, and I survey recent experimental and theoretical
examples. The insights and methods transfer also to novel superconducting and
metallic states. Of particular interest are critical quantum states, sometimes
found at quantum phase transitions, which have gapless excitations with no
particle- or wave-like interpretation, and control a significant portion of the
finite temperature phase diagram. Remarkably, their theory is connected to
holographic descriptions of Hawking radiation from black holes.Comment: 39 pages, 10 figures, review article for non-specialists; (v2) added
clarifications and references; (v3) minor corrections; (v4) added footnote on
hydrodynamic long-time tail
Interplay of Electron-Phonon Interaction and Electron Correlation in High Temperature Superconductivity
We study the electron-phonon interaction in the strongly correlated
superconducting cuprates. Two types of the electron-phonon interactions are
introduced in the model; the diagonal and off-diagonal interactions which
modify the formation energy of the Zhang-Rice singlet and its transfer
integral, respectively. The characteristic phonon-momentum and
electron-momentum dependence resulted from the off-diagonal coupling
can explain a variety of experiments. The vertex correction for the
electron-phonon interaction is formulated in the SU(2) slave-boson theory by
taking into account the collective modes in the superconducting ground states.
It is shown that the vertex correction enhances the attractive potential for
the d-wave paring mediated by phonon with around
which corresponds to the half-breathing mode of the oxygen
motion.Comment: 14 pages, 13 figure
Condensed matter and AdS/CFT
I review two classes of strong coupling problems in condensed matter physics,
and describe insights gained by application of the AdS/CFT correspondence. The
first class concerns non-zero temperature dynamics and transport in the
vicinity of quantum critical points described by relativistic field theories. I
describe how relativistic structures arise in models of physical interest,
present results for their quantum critical crossover functions and
magneto-thermoelectric hydrodynamics. The second class concerns symmetry
breaking transitions of two-dimensional systems in the presence of gapless
electronic excitations at isolated points or along lines (i.e. Fermi surfaces)
in the Brillouin zone. I describe the scaling structure of a recent theory of
the Ising-nematic transition in metals, and discuss its possible connection to
theories of Fermi surfaces obtained from simple AdS duals.Comment: 39 pages, 12 figures; Lectures at the 5th Aegean summer school, "From
gravity to thermal gauge theories: the AdS/CFT correspondence", and the De
Sitter Lecture Series in Theoretical Physics 2009, University of Groninge
Bond operator theory of doped antiferromagnets: from Mott insulators with bond-centered charge order, to superconductors with nodal fermions
The ground states and excitations of two-dimensional insulating and doped
Mott insulators are described by a bond operator formalism. While the method
represents the degrees of freedom of an arbitrary antiferromagnet exactly, it
is especially suited to systems in which there is a natural pairing of sites
into bonds, as in states with spontaneous or explicit spin-Peierls order (or
bond-centered charge order). In the undoped insulator, as discussed previously,
we obtain both paramagnetic and magnetically-ordered states. We describe the
evolution of superconducting order in the ground state with increasing
doping--at low doping, the superconductivity is weak, can co-exist with
magnetic order, and there are no gapless spin 1/2 fermionic excitations; at
high doping, the magnetic order is absent and we obtain a BCS d-wave
superconductor with gapless spin 1/2, nodal fermions. We present the critical
theory describing the onset of these nodal fermionic excitations. We discuss
the evolution of the spin spectrum, and obtain regimes where a spin 1 exciton
contributes a sharp resonance in the dynamic spin susceptiblity. We also
discuss the experimental consequences of low-energy, dynamically fluctuating,
spin-Peierls order in an isotropic CuO_2 plane--we compute consequences for the
damping and dispersion of an optical phonon involving primarily the O ions, and
compare the results with recent neutron scattering measurements of phonon
spectra.Comment: 16 pages + 14 pages of appendices, 18 figures; (v3) expanded
discussion of theory and experimental implications; (v4) Removed some
introductory review discussion and moved it to cond-mat/010823
Help-seeking behaviors for female sexual dysfunction: a cross sectional study from Iran
<p>Abstract</p> <p>Background</p> <p>Female sexual dysfunctions (FSD) are prevalent multifactor problems that in general remain misdiagnosed in primary health care. This population-based study investigated help-seeking behaviors among women with FSD in Iran.</p> <p>Methods</p> <p>This was a cross sectional study carried out in Kohgilouyeh-Boyer-Ahmad province in Iran. Using quota sampling all sexually active women aged 15 and over registered in primary health care delivery centers were studied. Experience of sexual problems was assessed using an ad-hoc questionnaire (Female sexual dysfunction: help-seeking behaviors survey) containing 14 items. Trained female nurses interviewed all participants after a verbal informed consent. Data were analyzed in a descriptive manner.</p> <p>Results</p> <p>In all 1540 women were studied. Of these, 786 (51%) cases had experienced at least one of the FSD problems. Results showed that 35.8% of women with FSD had sought no professional help and the most reasons for not seeking help were identified as: 'time constraints' and believing that it 'did not occur to me' (39.1 and 28.5% respectively). Sixty one percent of women who sought help for FSD reported that 'doctor gave me a definite diagnosis' and 'a definite treatment plan was given' in 57% of cases.</p> <p>Conclusion</p> <p>The study findings indicated that FSD problems were prevalent and many women did not seek help for their problem. Finding 'time constraints' and believing that the problem 'did not occur to me' as the most cited reasons for not seeking help might facilitate to understand potential barriers that exist in recognition and treatment of the female sexual dysfunctions. Since FSD might have a negative impact on interpersonal relationships and women's quality of life, it seems that there is need to address the problem both at local and national primary health care services.</p
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