2,934 research outputs found
Clinical Correlates of High Cervical Fractional Anisotropy in Acute Cervical Spinal Cord Injury
Objective: Fractional anisotropy (FA) of the high cervical cord (C1-C2), rostral to the injury site, correlates with upper limb function in patients with chronic cervical spinal cord injury (SCI). In acute cervical SCI, this relationship has not been investigated. The objective of this study was to identify functional correlates of FA of the high cervical cord in a series of patients with acute cervical SCI.
Methods: Traumatic cervical SCI patients who underwent presurgical cervical spine diffusion tensor imaging at our institution were reviewed for this study. FA of the whole cord as well as the lateralcorticospinal tracts (CSTs) was calculated on axial images from C1-C2. Upper limb motor (C5-T1) and sensory (C2-T1) function scores were extracted from the admission American Spinal Injury Association (ASIA) examinations. Correlation analysis for FA with ASIA examinations was performed using a Pearson correlation.
Results: Twelve subjects (9 men, 3 women; mean age 54.7 ± 4.0 years) underwent cervical spine diffusion tensor imaging at a mean duration of 3.6 ± 0.9 days postinjury. No patient had cord compression or intramedullary T2-weighted hyperintensities within the C1-C2 segments. FA correlated with upper limb motor score (whole cord: r = 0.59, P = .04; CST: 0.67, P = .01) and the ASIA grade (whole cord: r = 0.61, P = .03; CST: r = 0.71, P = .009). No correlation was found between FA and sensory scores.
Conclusions: FA of the whole cervical cord as well as the CST, rostral to the injury site, is associated with preserved upper limb motor function as well as superior ASIA grades after acute cervical SCI. FA of the high cervical cord is a potential biomarker of neural injury after acute cervical SCI
Analog of photon-assisted tunneling in a Bose-Einstein condensate
We study many-body tunneling of a small Bose-Einstein condensate in a
periodically modulated, tilted double-well potential. Periodic modulation of
the trapping potential leads to an analog of photon-assisted tunneling, with
distinct signatures of the interparticle interaction visible in the amount of
particles transferred from one well to the other. In particular, under
experimentally accessible conditions there exist well-developed half-integer
Shapiro-like resonances.Comment: 4 pages, 4 figures, RevTe
The Impact of Project-Based Learning on Student Content Knowledge in an Undergraduate, Teacher Preparatory, Foundations of Education Course
Presentation Poste
Diffusion Tensor Imaging Correlates with Short-Term Myelopathy Outcome in Patients with Cervical Spondylotic Myelopathy
Objective To determine if spinal cord diffusion tensor imaging indexes correlate with short-term clinical outcome in patients undergoing elective cervical spine surgery for cervical spondylotic myelopathy (CSM). Methods A prospective consecutive cohort study was performed in patients undergoing elective cervical spine surgery for CSM. After obtaining informed consent, patients with CSM underwent preoperative T2-weighted magnetic resonance imaging and diffusion tensor imaging of the cervical spine. Fractional anisotropy (FA) values at the level of maximum cord compression and at the noncompressed C1-2 level were calculated on axial images. We recorded the modified Japanese Orthopaedic Association (mJOA) scale, Neck Disability Index, and Short Form-36 physical functioning subscale scores for all patients preoperatively and 3 months postoperatively. Statistical analysis was performed to identify correlations between FA and clinical outcome scores. Results The study included 27 patients (mean age 54.5 years ± 1.9, 12 men). The mean postoperative changes in mJOA scale, Neck Disability Index, and Short Form-36 physical functioning subscale scores were 0.9 ± 0.3, −6.0 ± 1.9, and 3.4 ± 1.9. The mean FA at the level of maximum compression was significantly lower than the mean FA at the C1-2 level (0.5 vs. 0.55, P = 0.01). FA was significantly correlated with change in mJOA scale score (Pearson r = −0.42, P = 0.02). FA was significantly correlated with the preoperative mJOA scale score (Pearson r = 0.65, P \u3c 0.001). Conclusions Preoperative FA at the level of maximum cord compression significantly correlates with the 3-month change in mJOA scale score among patients with CSM. FA was also significantly associated with preoperative mJOA scale score and is a potential biomarker for spinal cord dysfunction in CSM
New Results from NA49
We present recent results of the SPS experiment NA49 on production of strange
particles and event-by-event fluctuations of mean and of charged particle
ratios in central Pb+Pb collisions at various beam energies (40, 80, 158 AGeV)
as well as in different collisions at 158 AGeV, going from p+p over light-ion
collisions to peripheral and central Pb+Pb.Comment: 5 pages, 6 figures (in eps) talk given at XXXI International
Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong China URL
http://ismd31.ccnu.edu.cn
Ground state energy of a homogeneous Bose-Einstein condensate beyond Bogoliubov
The standard calculations of the ground-state energy of a homogeneous Bose
gas rely on approximations which are physically reasonable but difficult to
control. Lieb and Yngvason [Phys. Rev. Lett. 80, 2504 (1998)] have proved
rigorously that the commonly accepted leading order term of the ground state
energy is correct in the zero-density-limit. Here, strong indications are given
that also the next to leading term is correct. It is shown that the first terms
obtained in a perturbative treatment provide contributions which are lost in
the Bogoliubov approach.Comment: 6 pages, accepted for publication in Europhys. Lett.
http://www.epletters.ch
Ground-state energy and depletions for a dilute binary Bose gas
When calculating the ground-state energy of a weakly interacting Bose gas
with the help of the customary contact pseudopotential, one meets an artifical
ultraviolet divergence which is caused by the incorrect treatment of the true
interparticle interactions at small distances. We argue that this problem can
be avoided by retaining the actual, momentum-dependent interaction matrix
elements, and use this insight for computing both the ground-state energy and
the depletions of a binary Bose gas mixture. Even when considering the
experimentally relevant case of equal masses of both species, the resulting
expressions are quite involved, and no straightforward generalizations of the
known single-species formulas. On the other hand, we demonstrate in detail how
these latter formulas are recovered from our two-species results in the limit
of vanishing interspecies interaction.Comment: 11 pages, Phys. Rev. A in pres
Interaction-dependent photon-assisted tunneling in optical lattices: a quantum simulator of strongly-correlated electrons and dynamical gauge fields
We introduce a scheme that combines photon-assisted tunneling by a moving optical lattice with strong Hubbard interactions, and allows for the quantum simulation of paradigmatic quantum many-body models. We show that, in a certain regime, this quantum simulator yields an effective Hubbard Hamiltonian with tunable bond-charge interactions, a model studied in the context of strongly-correlated electrons. In a different regime, we show how to exploit a correlated destruction of tunneling to explore Nagaoka ferromagnetism at finite Hubbard repulsion. By changing the photon-assisted tunneling parameters, we can also obtain a t-J model with independently controllable tunneling t, super-exchange interaction J, and even a Heisenberg-Ising anisotropy. Hence, the full phase diagram of this paradigmatic model becomes accessible to cold-atom experiments, departing from the region t _ J allowed by standard single-band Hubbard Hamiltonians in the strong-repulsion limit. We finally show that, by generalizing the photon-assisted tunneling scheme, the quantum simulator yields models of dynamical Gauge fields, where atoms of a given electronic state dress the tunneling of the atoms with a different internal state, leading to Peierls phases that mimic a dynamical magnetic field
Scaling property of the critical hopping parameters for the Bose-Hubbard model
Recently precise results for the boundary between the Mott insulator phase
and the superfluid phase of the homogeneous Bose-Hubbard model have become
available for arbitrary integer filling factor g and any lattice dimension d >
1. We use these data for demonstrating that the critical hopping parameters
obey a scaling relationship which allows one to map results for different g
onto each other. Unexpectedly, the mean-field result captures the dependence of
the exact critical parameters on the filling factor almost fully. We also
present an approximation formula which describes the critical parameters for d
> 1 and any g with high accuracy.Comment: 5 pages, 5 figures. to appear in EPJ
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