190 research outputs found
Observation of Droplet Size Oscillations in a Two-Phase Fluid under Shear Flow
Experimental observations of droplet size sustained oscillations are reported
in a two-phase flow between a lamellar and a sponge phase. Under shear flow,
this system presents two different steady states made of monodisperse
multilamellar droplets, separated by a shear-thinning transition. At low and
high shear rates, the droplet size results from a balance between surface
tension and viscous stress whereas for intermediate shear rates, it becomes a
periodic function of time. A possible mechanism for such kind of oscillations
is discussed
6-month multidisciplinary follow-up and outcomes of patients with paediatric inflammatory multisystem syndrome (PIMS-TS) at a UK tertiary paediatric hospital: a retrospective cohort study.
BACKGROUND: Paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) is a new, rare, post-infectious complication of SARS-CoV-2 infection in children. We aimed to describe the 6-month outcomes of PIMS-TS. METHODS: This retrospective cohort study comprised children (aged <18 years) who fulfilled the UK Royal College of Paediatrics and Child Health (RCPCH) diagnostic criteria for PIMS-TS and were admitted to Great Ormond Street Hospital (London, UK) between April 4 and Sept 1, 2020. Patients were followed up by a multidisciplinary team of specialists at 6 weeks and 6 months after admission. Biochemical and functional outcomes were analysed. FINDINGS: 46 children were included in this study. The median age at presentation was 10·2 years (IQR 8·8-13·3), 30 (65%) patients were male and 16 (35%) were female, 37 (80%) were from minority ethnic groups, and eight (17%) had pre-existing comorbidities. All patients had elevated markers of systemic inflammation at baseline. None of the patients died. By 6 months, systemic inflammation was resolved in all but one patient. 38 (90%) of 42 patients who had positive SARS-CoV-2 IgG antibodies within 6 weeks of admission remained seropositive at 6 months. Echocardiograms were normal in 44 (96%) of 46 patients by 6 months, and gastrointestinal symptoms that were reported in 45 (98%) of 46 patients at onset were present in six (13%) of 46 patients at 6 months. Renal, haematological, and otolaryngological findings largely resolved by 6 months. Although minor abnormalities were identified on neurological examination in 24 (52%) of 46 patients at 6 weeks and in 18 (39%) of 46 at 6 months, we found minimal functional impairment at 6 months (median Expanded Disability Status Scale score 0 [IQR 0-1]). Median manual muscle test-8 scores improved from 53 (IQR 43-64) during hospital admission to 80 (IQR 68-80) at 6 months, but 18 (45%) of 40 patients showed 6-min walk test results below the third centile for their age or sex at 6 months. PedsQL responses revealed severe emotional difficulties at 6 months (seven [18%] of 38 by parental report and eight [22%] of 38 by self report). 45 (98%) of 46 patients were back in full-time education (virtually or face to face) by 6 months. INTERPRETATION: Despite initial severe illness, few organ-specific sequelae were observed at 6 months. Ongoing concerns requiring physical re-conditioning and mental health support remained, and physiotherapy assessments revealed persisting poor exercise tolerance. Longer-term follow-up will help define the extended natural history of PIMS-TS. FUNDING: None
Collective oscillations of a 1D trapped Bose gas
Starting from the hydrodynamic equations of superfluids, we calculate the
frequencies of the collective oscillations of a harmonically trapped Bose gas
for various 1D configurations. These include the mean field regime described by
Gross-Pitaevskii theory and the beyond mean field regime at small densities
described by Lieb-Liniger theory. The relevant combinations of the physical
parameters governing the transition between the different regimes are
discussed.Comment: 4 pages, 2 figure
Gravitational collapse with tachyon field and barotropic fluid
A particular class of space-time, with a tachyon field, \phi, and a
barotropic fluid constituting the matter content, is considered herein as a
model for gravitational collapse. For simplicity, the tachyon potential is
assumed to be of inverse square form i.e., V(\phi) \sim \phi^{-2}. Our purpose,
by making use of the specific kinematical features of the tachyon, which are
rather different from a standard scalar field, is to establish the several
types of asymptotic behavior that our matter content induces. Employing a
dynamical system analysis, complemented by a thorough numerical study, we find
classical solutions corresponding to a naked singularity or a black hole
formation. In particular, there is a subset where the fluid and tachyon
participate in an interesting tracking behaviour, depending sensitively on the
initial conditions for the energy densities of the tachyon field and barotropic
fluid. Two other classes of solutions are present, corresponding respectively,
to either a tachyon or a barotropic fluid regime. Which of these emerges as
dominant, will depend on the choice of the barotropic parameter, \gamma.
Furthermore, these collapsing scenarios both have as final state the formation
of a black hole.Comment: 18 pages, 7 figures. v3: minor changes. Final version to appear in
GR
Sensitivity of a tonne-scale NEXT detector for neutrinoless double beta decay searches
The Neutrino Experiment with a Xenon TPC (NEXT) searches for the neutrinoless
double-beta decay of Xe-136 using high-pressure xenon gas TPCs with
electroluminescent amplification. A scaled-up version of this technology with
about 1 tonne of enriched xenon could reach in less than 5 years of operation a
sensitivity to the half-life of neutrinoless double-beta decay decay better
than 1E27 years, improving the current limits by at least one order of
magnitude. This prediction is based on a well-understood background model
dominated by radiogenic sources. The detector concept presented here represents
a first step on a compelling path towards sensitivity to the parameter space
defined by the inverted ordering of neutrino masses, and beyond.Comment: 22 pages, 11 figure
Improvement of xylanase production by a parasexual cross between Aspergillus niger strains
Quantum Magnetism of Spin-Ladder Compounds with Trapped-Ion Crystals
The quest for experimental platforms that allow for the exploration, and even
control, of the interplay of low dimensionality and frustration is a
fundamental challenge in several fields of quantum many-body physics, such as
quantum magnetism. Here, we propose the use of cold crystals of trapped ions to
study a variety of frustrated quantum spin ladders. By optimizing the trap
geometry, we show how to tailor the low dimensionality of the models by
changing the number of legs of the ladders. Combined with a method for
selectively hiding of ions provided by laser addressing, it becomes possible to
synthesize stripes of both triangular and Kagome lattices. Besides, the degree
of frustration of the phonon-mediated spin interactions can be controlled by
shaping the trap frequencies. We support our theoretical considerations by
initial experiments with planar ion crystals, where a high and tunable
anisotropy of the radial trap frequencies is demonstrated. We take into account
an extensive list of possible error sources under typical experimental
conditions, and describe explicit regimes that guarantee the validity of our
scheme
Intracranial Aneurysm Classifier Using Phenotypic Factors: An International Pooled Analysis
Intracranial aneurysms (IAs) are usually asymptomatic with a low risk of rupture, but consequences of aneurysmal subarachnoid hemorrhage (aSAH) are severe. Identifying IAs at risk of rupture has important clinical and socio-economic consequences. The goal of this study was to assess the effect of patient and IA characteristics on the likelihood of IA being diagnosed incidentally versus ruptured. Patients were recruited at 21 international centers. Seven phenotypic patient characteristics and three IA characteristics were recorded. The analyzed cohort included 7992 patients. Multivariate analysis demonstrated that: (1) IA location is the strongest factor associated with IA rupture status at diagnosis; (2) Risk factor awareness (hypertension, smoking) increases the likelihood of being diagnosed with unruptured IA; (3) Patients with ruptured IAs in high-risk locations tend to be older, and their IAs are smaller; (4) Smokers with ruptured IAs tend to be younger, and their IAs are larger; (5) Female patients with ruptured IAs tend to be older, and their IAs are smaller; (6) IA size and age at rupture correlate. The assessment of associations regarding patient and IA characteristics with IA rupture allows us to refine IA disease models and provide data to develop risk instruments for clinicians to support personalized decision-making
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