3,937 research outputs found

    Quantitative sensory testing in painful hand osteoarthritis demonstrates features of peripheral sensitisation.

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    Hand osteoarthritis (HOA) is a prevalent condition for which treatments are based on analgesia and physical therapies. Our primary objective was to evaluate pain perception in participants with HOA by assessing the characteristics of nodal involvement, pain threshold in each hand joint, and radiological severity. We hypothesised that inflammation in hand osteoarthritis joints enhances sensitivity and firing of peripheral nociceptors, thereby causing chronic pain. Participants with proximal and distal interphalangeal (PIP and DIP) joint HOA and non-OA controls were recruited. Clinical parameters of joint involvement were measured including clinical nodes, VAS (visual analogue score) for pain (0-100 mm scale), HAQ (health assessment questionnaire), and Kellgren-Lawrence scores for radiological severity and pain threshold measurement were performed. The mean VAS in HOA participants was 59.3 mm ± 8.19 compared with 4.0 mm ± 1.89 in the control group (P < 0.0001). Quantitative sensory testing (QST) demonstrated lower pain thresholds in DIP/PIP joints and other subgroups in the OA group including the thumb, metacarpophalangeal (MCPs), joints, and wrists (P < 0.008) but not in controls (P = 0.348). Our data demonstrate that HOA subjects are sensitised to pain due to increased firing of peripheral nociceptors. Future work to evaluate mechanisms of peripheral sensitisation warrants further investigation

    Temperature effects on the magnetization of quasi-one-dimensional Peierls distorted materials

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    It is shown that temperature acts to disrupt the magnetization of Peierls distorted quasi-one-dimensional materials (Q1DM). The mean-field finite temperature phase diagram for the field theory model employed is obtained by considering both homogeneous and inhomogeneous condensates. The tricritical points of the second order transition lines of the gap parameter and magnetization are explicitly calculated. It is also shown that in the absence of an external static magnetic field the magnetization is always zero, at any temperature. As expected, temperature does not induce any magnetization effect on Peierls distorted Q1DM.Comment: 11 pages, 2 figure

    Electron and ion kinetic effects in the saturation of a driven ion acoustic wave

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    The role of ion and electron kinetic effects is investigated in the context of the nonlinear saturation of a driven ion acoustic wave(IAW) and its parametric decay into subharmonics. The simulations are carried out with a full–particle-in-cell (PIC) code, in which both ions and electrons are treated kinetically. The full-PIC results are compared with those obtained from a hybrid-PIC code (kinetic ions and Boltzmann electrons). It is found that the largest differences between the two kinds of simulations take place when the IAW is driven above the ion wave-breaking limit. In such a case of a strong drive, the hybrid-PIC simulations lead to a Berstein-Greene-Kruskal-like nonlinear IAW of a large amplitude, while in the full-PIC the IAW amplitude decays to a small level after a transient stage. The electron velocity distribution function is significantly flattened in the domain of small electron velocities. As a result the nonlinear frequency shift due to the electron kinetic effects compensates partly the nonlinear frequency shift due to the ion kinetic effects, allowing then for the parametric decay of the driven IAW into subharmonics. These observations lead to the conclusion that electron kinetic effects become important whenever the nonlinear effects come into play

    A global simulation for laser driven MeV electrons in 50μm50\mu m-diameter fast ignition targets

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    The results from 2.5-dimensional Particle-in-Cell simulations for the interaction of a picosecond-long ignition laser pulse with a plasma pellet of 50-μm\mu m diameter and 40 critical density are presented. The high density pellet is surrounded by an underdense corona and is isolated by a vacuum region from the simulation box boundary. The laser pulse is shown to filament and create density channels on the laser-plasma interface. The density channels increase the laser absorption efficiency and help generate an energetic electron distribution with a large angular spread. The combined distribution of the forward-going energetic electrons and the induced return electrons is marginally unstable to the current filament instability. The ions play an important role in neutralizing the space charges induced by the the temperature disparity between different electron groups. No global coalescing of the current filaments resulted from the instability is observed, consistent with the observed large angular spread of the energetic electrons.Comment: 9 pages, 6 figures, to appear in Physics of Plasmas (May 2006

    Quantum normal-to-inhomogeneous superconductor phase transition in nearly two-dimensional metals

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    In multi-band systems, electrons from different orbitals coexist at the Fermi surface. An attractive interaction among these quasi-particles gives rise to inter-band or hybrid pairs which eventually condense in a superconducting state. These quasi-particles have a natural mismatch of their Fermi wave-vectors, δkF\delta k_F, which depends on the strength of the hybridization between their orbitals. The existence of this natural scale suggests the possibility of inhomogeneous superconducting ground states in these systems, even in the absence of an applied magnetic field. Furthermore, since hybridization VV depends on pressure, this provides an external parameter to control the wave-vectors mismatch at the Fermi surface. In this work, we study the phase diagram of a two-dimensional, two-band metal with inter-band pairing. We show that as the mismatch between the Fermi wave-vectors of the two hybrid bands is reduced, the system presents a normal-to-inhomogeneous superconductor quantum phase transition at a critical value of the hybridization Vc=Δ0V_c=\Delta_0. The superconducting ground state for V<VcV<V_c is characterized by a wave-vector with magnitude qc=qc=2Δ0/vˉf|\mathbf{q}_c|=q_c=2 \Delta_0/\bar{v}_f. Here Δ0\Delta_0 is the superconducting gap in the homogeneous state and vˉf\bar{v}_f the average Fermi velocity. We discuss the nature of the quantum critical point (QCP) at VcV_c and obtain the associated quantum critical exponents.Comment: 6 pages, 4 figure

    Adolescent over-general memory, life events and mental health outcomes: Findings from a UK cohort study

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    Previous research suggesting that over-general memory (OGM) may moderate the effect of life events on depressive symptoms and suicidality has sampled older adolescents or adults, or younger adolescents in high-risk populations, and has been conducted over relatively short follow-up periods. The authors examined the relationship between OGM at age 13 and life events and mental health outcomes (depression, self-harm, suicidal ideation and planning) at age 16 years within a sample of 5792 adolescents participating in the Avon Longitudinal Study of Parents and Children (ALSPAC), approximately 3800 of whom had also provided data on depression and self-harm. There was no clear evidence of either direct or interactive effects of OGM at age 13 on levels of depression at age 16. Similarly there was no clear evidence of either direct or interactive effects of OGM on suicidal ideation and self-harm. Although there was some evidence that over-general autobiographical memory was associated with reduced risk of suicidal planning and increased risk of self-harm, these associations were absent when confounding variables were taken into account. The findings imply that although OGM is a marker of vulnerability to depression and related psychopathology in high-risk groups, this cannot be assumed to generalise to whole populations

    Phase Transition in Asymmetrical Superfluids I: Equal Fermi Surfaces

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    In this paper, we study phase transitions in asymmetrical fermion superfluids. In this scenario, the candidates to form pair are particles with mismatched masses and chemical potentials. We derive an expression for the critical temperature in terms of the gap and masses (or chemical potentials) when the constraint of equal Fermi surfaces maμa=mbμbm_a\mu_a = m_b\mu_b is imposed.Comment: RevTex, 11 pages, 2 figures, typos corrected and an appendix added, accepted for publication in Phys. Rev.
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