38 research outputs found
Persistence of entanglement in thermal states of spin systems
We study and compare the persistence of bipartite entanglement (BE) and
multipartite entanglement (ME) in one-dimensional and two-dimensional spin XY
models in an external transverse magnetic field under the effect of thermal
excitations. We compare the threshold temperature at which the entanglement
vanishes in both types of entanglement. We use the entanglement of formation as
a measure of the BE and the geometric measure to evaluate the ME of the system.
We have found that in both dimensions in the anisotropic and partially
anisotropic spin systems at zero temperatures, all types of entanglement decay
as the magnetic field increases but are sustained with very small magnitudes at
high field values. Also we found that for the same systems, the threshold
temperatures of the nearest neighbour (nn) BEs are higher than both of the
next-to-nearest neighbour BEs and MEs and the three of them increase
monotonically with the magnetic field strength. Thus, as the temperature
increases, the ME and the far parts BE of the system become more fragile to
thermal excitations compared to the nn BE. For the isotropic system, all types
of entanglement and threshold temperatures vanish at the same exact small value
of the magnetic field. We emphasise the major role played by both the
properties of the ground state of the system and the energy gap in controlling
the characteristics of the entanglement and threshold temperatures. In
addition, we have shown how an inserted magnetic impurity can be used to
preserve all types of entanglement and enhance their threshold temperatures.
Furthermore, we found that the quantum effects in the spin systems can be
maintained at high temperatures, as the different types of entanglements in the
spin lattices are sustained at high temperatures by applying sufficiently high
magnetic fields.Comment: 20 pages, 17 figure
Real time optimum trajectory generation for redundant/hyper-redundant serial industrial manipulators
Linear Lattice and Trajectory Reconstruction and Correction at FAST Linear Accelerator
The low energy part of the FAST linear accelerator based on 1.3 GHz
superconducting RF cavities was successfully commissioned. During
commissioning, beam based model dependent methods were used to correct linear
lattice and trajectory. Lattice correction algorithm is based on analysis of
beam shape from profile monitors and trajectory responses to dipole correctors.
Trajectory responses to field gradient variations in quadrupoles and phase
variations in superconducting RF cavities were used to correct bunch offsets in
quadrupoles and accelerating cavities relative to their magnetic axes. Details
of used methods and experimental results are presented.Comment: 3 p
The 'Switch' study protocol: a randomised-controlled trial of switching to an alternative tumour-necrosis factor (TNF)-inhibitor drug or abatacept or rituximab in patients with rheumatoid arthritis who have failed an initial TNF-inhibitor drug
Background: Rheumatoid Arthritis (RA) is one of the most common autoimmune diseases, affecting approximately 1% of the UK adult population. Patients suffer considerable pain, stiffness and swelling and can sustain various degrees of joint destruction, deformity, and significant functional decline. In addition, the economic burden due to hospitalisation and loss of employment is considerable, with over 50% of patients being work-disabled within 10 years of diagnosis. Despite several biologic disease modifying anti-rheumatic drugs (bDMARD) now available, there is a lack of data to guide biologic sequencing. In the UK, second-line biologic treatment is restricted to a single option, rituximab. The aim of the SWITCH trial is to establish whether an alternative-mechanism-TNF-inhibitor (TNFi) or abatacept are as effective as rituximab in patients with RA who have failed an initial TNFi drug. Methods/Design: SWITCH is a pragmatic, phase IV, multi-centre, parallel-group design, open-label, randomised, controlled trial (RCT) comparing alternative-mechanism-TNFi and abatacept with rituximab in patients with RA who have failed an initial TNFi drug. Participants are randomised in a 1:1:1 ratio to receive alternative mechanism TNFi, (monoclonal antibodies: infliximab, adalimumab, certolizumab or golimumab or the receptor fusion protein, etanercept), abatacept or rituximab during the interventional phase (from randomisation up to week 48). Participants are subsequently followed up to a maximum of 96 weeks, which constitutes the observational phase. The primary objective is to establish whether an alternative-mechanism-TNFi or abatacept are non-inferior to rituximab in terms of disease response at 24 weeks post randomisation. The secondary objectives include the comparison of alternative-mechanism-TNFi and abatacept to rituximab in terms of disease response, quality of life, toxicity, safety and structural and bone density outcomes over a 12-month period (48 weeks) and to evaluate the cost-effectiveness of switching patients to alternative active therapies compared to current practice. Discussion: SWITCH is a well-designed trial in this therapeutic area that aims to develop a rational treatment algorithm to potentially inform personalised treatment regimens (as opposed to switching all patients to only one available (and possibly unsuccessful) therapy), which may lead to long-term improved patient outcomes and gains in population health