11,726 research outputs found
Suspending test masses in terrestrial millihertz gravitational-wave detectors: a case study with a magnetic assisted torsion pendulum
Current terrestrial gravitational-wave detectors operate at frequencies above
10 Hz. There is strong astrophysical motivation to construct low-frequency
gravitational-wave detectors capable of observing 10 mHz - 10Hz signals. While
space-based detectors provide one means of achieving this end, one may also
consider terretrial detectors. However, there are numerous technological
challenges. In particular, it is difficult to isolate test masses so that they
are both seismically isolated and freely falling under the influence of gravity
at millihertz frequencies. We investigate the challenges of low-frequency
suspension in a hypothetical terrestrial detector. As a case study, we consider
a Magnetically Assisted Gravitational-wave Pendulum Intorsion (MAGPI)
suspension design. We construct a noise budget to estimate some of the required
specifications. In doing so, we identify what are likely to be a number of
generic limiting noise sources for terrestrial millihertz gravitational-wave
suspension systems (as well as some peculiar to the MAGPI design). We highlight
significant experimental challenges in order to argue that the development of
millihertz suspensions will be a daunting task. Any system that relies on
magnets faces even greater challenges. Entirely mechanical designs such as
Zollner pendulums may provide the best path forward.Comment: 6 pages, 4 figure
Formation of Random Dark Envelope Solitons from Incoherent Waves
This letter reports experimental results on a new type of soliton: the random
temporal dark soliton. One excites an incoherent large-amplitude propagating
spin-wave packet in a ferromagnetic film strip with a repulsive, instantaneous
nonlinearity. One then observes the random formation of dark solitons from this
wave packet. The solitons appear randomly in time and in position relative to
the entire wave packet. They can be gray or black. For wide and/or very strong
spin-wave packets, one also observes multiple dark solitons. In spite of the
randomness of the initial wave packets and the random formation processes, the
solitons show signatures that are found for conventional coherent dark
solitons.Comment: 10 pages, 4 figures, double-spaced preprint forma
Hartree-Fock-Bogoliubov Model and Simulation of Attractive and Repulsive Bose-Einstein Condensates
We describe a model of dynamic Bose-Einstein condensates near a Feshbach
resonance that is computationally feasible under assumptions of spherical or
cylindrical symmetry. Simulations in spherical symmetry approximate the
experimentally measured time to collapse of an unstably attractive condensate
only when the molecular binding energy in the model is correct, demonstrating
that the quantum fluctuations and atom-molecule pairing included in the model
are the dominant mechanisms during collapse. Simulations of condensates with
repulsive interactions find some quantitative disagreement, suggesting that
pairing and quantum fluctuations are not the only significant factors for
condensate loss or burst formation. Inclusion of three-body recombination was
found to be inconsequential in all of our simulations, though we do not
consider recent experiments [1] conducted at higher densities
Peptide redesign for inhibition of the complement system: Targeting age-related macular degeneration.
PurposeTo redesign a complement-inhibiting peptide with the potential to become a therapeutic for dry and wet age-related macular degeneration (AMD).MethodsWe present a new potent peptide (Peptide 2) of the compstatin family. The peptide is developed by rational design, based on a mechanistic binding hypothesis, and structural and physicochemical properties derived from molecular dynamics (MD) simulation. The inhibitory activity, efficacy, and solubility of Peptide 2 are evaluated using a hemolytic assay, a human RPE cell-based assay, and ultraviolet (UV) absorption properties, respectively, and compared to the respective properties of its parent peptide (Peptide 1).ResultsThe sequence of Peptide 2 contains an arginine-serine N-terminal extension (a characteristic of parent Peptide 1) and a novel 8-polyethylene glycol (PEG) block C-terminal extension. Peptide 2 has significantly improved aqueous solubility compared to Peptide 1 and comparable complement inhibitory activity. In addition, Peptide 2 is more efficacious in inhibiting complement activation in a cell-based model that mimics the pathobiology of dry AMD.ConclusionsWe have designed a new peptide analog of compstatin that combines N-terminal polar amino acid extensions and C-terminal PEGylation extensions. This peptide demonstrates significantly improved aqueous solubility and complement inhibitory efficacy, compared to the parent peptide. The new peptide overcomes the aggregation limitation for clinical translation of previous compstatin analogs and is a candidate to become a therapeutic for the treatment of AMD
Communication and Low Mood (CALM): a randomized controlled trial of behavioural therapy for stroke patients with aphasia
Objective:
The aim was to evaluate behavioural therapy as a treatment for low mood in people with aphasia.
Design:
A randomized controlled trial comparing behavioural therapy plus usual care with a usual care control. Potential participants with aphasia after stroke were screened for the presence of low mood. Those who met the criteria and gave consent were randomly allocated.
Setting:
Participants were recruited from hospital wards, community rehabilitation, speech and language therapy services and stroke groups.
Subjects:
Of 511 people with aphasia identified, 105 had low mood and were recruited.
Interventions:
Behavioural therapy was offered for up to three months. Outcomes were assessed three and six months after random allocation.
Main measures:
Stroke Aphasic Depression Questionnaire, Visual Analog Mood Scales ‘sad’ item, and Visual Analogue Self-Esteem Scale.
Results:
Participants were aged 29 to 94 years (mean 67.0, SD 13.5) and 66 (63%) were men. Regression analysis showed that at three months, when baseline values and communication impairment were controlled for, group allocation was a significant predictor of the Stroke Aphasic Depression Questionnaire (P < 0.05), visual analogue ‘sad’ (P = 0.03), and Visual Analogue Self-Esteem Scale (P < 0.01). At six months, group alone was a significant predictor of the Stroke Aphasic Depression Questionnaire (P < 0.05), and remained significant when baseline values were controlled for (P = 0.02). Mean Stroke Aphasic Depression Questionnaire 10-item hospital version scores decreased from baseline to six months by six points in the intervention group as compared with an increase of 1.9 points in the control group.
Conclusions:
Behavioural therapy seemed to improve the mood of people with aphasia
Observation of Spin Wave Soliton Fractals in Magnetic Film Active Feedback Rings
The manifestation of fractals in soliton dynamics has been observed for the
first time. The experiment utilized self-generated spin wave envelope solitons
in a magnetic film based active feedback ring. At high ring gain, the soliton
that circulates in the ring breathes in a fractal pattern. The corresponding
power frequency spectrum shows a comb structure, with each peak in the comb
having its own comb, and so on, to finer and finer scales.Comment: 4 pages, 4 figure
The purpose of mess in action research: building rigour though a messy turn
Mess and rigour might appear to be strange bedfellows. This paper argues that the purpose of mess is to facilitate a turn towards new constructions of knowing that lead to transformation in practice (an action turn). Engaging in action research - research that can disturb both individual and communally held notions of knowledge for practice - will be messy. Investigations into the 'messy area', the interface between the known and the nearly known, between knowledge in use and tacit knowledge as yet to be useful, reveal the 'messy area' as a vital element for seeing, disrupting, analysing, learning, knowing and changing. It is the place where long-held views shaped by professional knowledge, practical judgement, experience and intuition are seen through other lenses. It is here that reframing takes place and new knowing, which has both theoretical and practical significance, arises: a 'messy turn' takes place
Citizen surveil-labour: Analysing Crime Stoppers and its alliance of police, media, and publics
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