391 research outputs found
Endometrial osseous metaplasia: clinicopathological study of a case and literature review
Endometrial ossification is a rare clinical condition related to menstrual disturbances and infertility. Its etiology and pathogenesis are controversial. The commonly accepted hypothesis is that ossification represents retained fetal bones following spontaneous or therapeutic abortion suggesting enchondral ossification. It can also be due to transformation of mesenchymal tissue to bone in response to chronic inflammation. We present one such case in a 41 year old woman who presented with menorrhagia and dysmenorrhoea following induced abortion 16 years back at 12 weeks of gestation. The patient underwent hysterectomy. We also present a literature review
Coulombian Disorder in Periodic Systems
We study the effect of unscreened charged impurities on periodic systems. We
show that the long wavelength component of the disorder becomes long ranged and
dominates static correlation functions. On the other hand, because of the
statistical tilt symmetry, dynamical properties such as pinning remain
unaffected. As a concrete example, we focus on the effect of Coulombian
disorder generated by charged impurities, on 3D charge density waves with non
local elasticity. We calculate the x-ray intensity and find that it is
identical to the one produced by thermal fluctuations in a disorder-free
smectic-A. We discuss the consequences of these results for experiments.Comment: 11 pages, 3 figures, revtex
A non-Hermitian critical point and the correlation length of strongly correlated quantum systems
We study a non-Hermitian generalization of quantum systems in which an
imaginary vector potential is added to the momentum operator. In the
tight-binding approximation, we make the hopping energy asymmetric in the
Hermitian Hamiltonian. In a previous article, we conjectured that the
non-Hermitian critical point where the energy gap vanishes is equal to the
inverse correlation length of the Hermitian system and we confirmed the
conjecture for two exactly solvable systems. In this article, we present more
evidence for the conjecture. We also argue the basis of our conjecture by
noting the dispersion relation of the elementary excitation.Comment: 25 pages, 18 figure
Non-Abelian bosonization of the frustrated antiferromagnetic spin-1/2 chain
We study the spin-1/2 chain with nearest neighbor () and
next-nearest neighbor () interactions in the regime , which is equivalent to two chains with a `zig-zag' interaction. In
the continuum limit, this system is described in term of two coupled level-1
WZW field theories. We illustrate its equivalence with four off-critical Ising
models (Majorana fermions). This description is used to investigate the opening
of a gap as a function of and the associated spontaneous breakdown
of parity. We calculate the dynamic spin structure factor near the wavevectors
accessible to the continuum limit. We comment on the nonzero string order
parameter and show the presence of a hidden
symmetry via a nonlocal transformation on the microscopic Hamiltonian. For a
ferromagnetic interchain coupling, the model is conjectured to be critical,
with different velocities for the spin singlet and spin triplet excitations.Comment: 20 pages, RevTeX, 1 postscript figure. Minor corrections added,
resulting in different velocity renormalizations; no qualitative change in
conclusion
Baseline patient characteristics associated with response to biologic therapy in patients with psoriatic arthritis enrolled in the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.
Objectives: To compare baseline characteristics between patients with psoriatic arthritis (PsA) who achieved and did not achieve minimal disease activity (MDA) with biologic therapy in the US-based Corrona Psoriatic Arthritis/Spondyloarthritis Registry.
Methods: Patients with PsA aged ≥18 years enrolled between March 2013 and March 2016 who were receiving biologics at enrolment (baseline), not in MDA and had ≥2 follow-up visits were included. Patients were classified as those who remained on their index biologic and achieved MDA at the second follow-up visit (MDA achievers (MDA-A)) and those who did not (MDA non-achievers (MDA-NA)). Demographics, clinical characteristics, patient-reported outcomes and medication history were compared between groups.
Results: Of 148 patients with PsA who met the inclusion criteria, 34 (23.0%) and 114 (77.0%) were classified as MDA-A and MDA-NA, respectively. At baseline, most patients (96.6%) were receiving tumour necrosis factor inhibitors, and both groups were similar in age, sex, race, medication history, enthesitis and dactylitis counts, disease duration and comorbidities. Compared with MDA-A, MDA-NA had significantly worse mean tender joint count (7.2 vs 3.4), patient-reported pain (51.2 vs 35.7), patient-reported fatigue (54.1 vs 42.4), physical function (Health Assessment Questionnaire, 1.0 vs 0.6), Bath Ankylosing Disease Activity Index (5.0 vs 3.4) and Bath Ankylosing Spondylitis Functional Index (4.0 vs 2.0) scores (all p\u3c0.05).
Conclusions: Approximately one in four patients achieved MDA with their index biologic at the time of the second follow-up visit. Both groups were similar in several baseline demographic and clinical features; however, patients who did not achieve MDA generally had worse tender joint counts and patient-reported outcomes
Dynamical Structure Factors of the S=1/2 Bond-Alternating Spin Chain with a Next-Nearest-Neighbor Interaction in Magnetic Fields
The dynamical structure factor of the S=1/2 bond-alternating spin chain with
a next-nearest-neighbor interaction in magnetic field is investigated using the
continued fraction method based on the Lanczos algorithm. When the plateau
exists on the magnetization curve, the longitudinal dynamical structure factor
shows a large intensity with a periodic dispersion relation, while the
transverse one shows a large intensity with an almost dispersionless mode. The
periodicity and the amplitude of the dispersion relation in the longitudinal
dynamical structure factor are sensitive to the coupling constants. The
dynamical structure factor of the S=1/2 two-leg ladder in magnetic field is
also calculated in the strong interchain-coupling regime.
The dynamical structure factor shows gapless or gapful behavior depending on
the wave vector along the rung.Comment: 8 pages, 4 figures, to appear in Journal of the Physical Society of
Japan, vol. 69, no. 10, (2000
Numerical and approximate analytical results for the frustrated spin-1/2 quantum spin chain
We study the frustrated phase of the quantum spin-
system with nearest-neighbour and next-nearest-neighbour isotropic exchange
known as the Majumdar-Ghosh Hamiltonian. We first apply the coupled-cluster
method of quantum many-body theory based on a spiral model state to obtain the
ground state energy and the pitch angle. These results are compared with
accurate numerical results using the density matrix renormalisation group
method, which also gives the correlation functions. We also investigate the
periodicity of the phase using the Marshall sign criterion. We discuss
particularly the behaviour close to the phase transitions at each end of the
frustrated phase.Comment: 17 pages, Standard Latex File + 7 PostScript figures in separate
file. Figures also can also be requested from [email protected]
Impact of long-range interactions on the disordered vortex lattice
The interaction between the vortex lines in a type-II superconductor is
mediated by currents. In the absence of transverse screening this interaction
is long-ranged, stiffening up the vortex lattice as expressed by the dispersive
elastic moduli. The effect of disorder is strongly reduced, resulting in a
mean-squared displacement correlator =
characterized by a mere logarithmic growth with distance. Finite screening cuts
the interaction on the scale of the London penetration depth \lambda and limits
the above behavior to distances R<\lambda. Using a functional renormalization
group (RG) approach, we derive the flow equation for the disorder correlation
function and calculate the disorder-averaged mean-squared relative displacement
\propto ln^{2\sigma} (R/a_0). The logarithmic growth (2\sigma=1) in
the perturbative regime at small distances [A.I. Larkin and Yu.N. Ovchinnikov,
J. Low Temp. Phys. 34, 409 (1979)] crosses over to a sub-logarithmic growth
with 2\sigma=0.348 at large distances.Comment: 9 pages, no figure
Behavior of a frustrated quantum spin chain with bond dimerization
We clarified behavior of the excitation gap in a frustrated S=1/2 quantum
spin chain with bond dimerization by using the numerical diagonalization of
finite systems and a variational approach. The model interpolates between the
independent dimer model and the S=1 spin chain by changing a strength of the
dimerization. The energy gap is minimum at the fully-frustrated point, where a
localized kink and a freely mobile anti-kink govern the low-lying excitations.
Away from the point, a kink and an antikink form a bound state by an effective
triangular potential between them. The consequential gap enhancement and the
localization length of the bound state is obtained exactly in the continuous
limit. The gap enhancement obeys a power law with exponent 2/3. The method and
the obtained results are common to other frustrated double spin-chain systems,
such as the one-dimensional J_1 - J_2 model, or the frustrated ladder model.Comment: 11 pages, REVTeX, 8 figures in eps-fil
Frustrated quantum Heisenberg ferrimagnetic chains
We study the ground-state properties of weakly frustrated Heisenberg
ferrimagnetic chains with nearest and next-nearest neighbor antiferromagnetic
exchange interactions and two types of alternating sublattice spins S_1 > S_2,
using 1/S spin-wave expansions, density-matrix renormalization group, and
exact- diagonalization techniques. It is argued that the zero-point spin
fluctuations completely destroy the classical commensurate- incommensurate
continuous transition. Instead, the long-range ferrimagnetic state disappears
through a discontinuous transition to a singlet state at a larger value of the
frustration parameter. In the ferrimagnetic phase we find a disorder point
marking the onset of incommensurate real-space short-range spin-spin
correlations.Comment: 16 pages (LaTex 2.09), 6 eps figure
- …