2,323 research outputs found
Acoustic calibration apparatus for calibrating plethysmographic acoustic pressure sensors
An apparatus for calibrating an acoustic sensor is described. The apparatus includes a transmission material having an acoustic impedance approximately matching the acoustic impedance of the actual acoustic medium existing when the acoustic sensor is applied in actual in-service conditions. An elastic container holds the transmission material. A first sensor is coupled to the container at a first location on the container and a second sensor coupled to the container at a second location on the container, the second location being different from the first location. A sound producing device is coupled to the container and transmits acoustic signals inside the container
Direct Evidence for a Magnetic f-electron Mediated Cooper Pairing Mechanism of Heavy Fermion Superconductivity in CeCoIn5
To identify the microscopic mechanism of heavy-fermion Cooper pairing is an
unresolved challenge in quantum matter studies; it may also relate closely to
finding the pairing mechanism of high temperature superconductivity.
Magnetically mediated Cooper pairing has long been the conjectured basis of
heavy-fermion superconductivity but no direct verification of this hypothesis
was achievable. Here, we use a novel approach based on precision measurements
of the heavy-fermion band structure using quasiparticle interference (QPI)
imaging, to reveal quantitatively the momentum-space (k-space) structure of the
f-electron magnetic interactions of CeCoIn5. Then, by solving the
superconducting gap equations on the two heavy-fermion bands
with these magnetic interactions as mediators of the
Cooper pairing, we derive a series of quantitative predictions about the
superconductive state. The agreement found between these diverse predictions
and the measured characteristics of superconducting CeCoIn5, then provides
direct evidence that the heavy-fermion Cooper pairing is indeed mediated by the
f-electron magnetism.Comment: 19 pages, 4 figures, Supplementary Information: 31 pages, 5 figure
Anisotropic Energy Gaps of Iron-based Superconductivity from Intra-band Quasiparticle Interference in LiFeAs
If strong electron-electron interactions between neighboring Fe atoms mediate
the Cooper pairing in iron-pnictide superconductors, then specific and distinct
anisotropic superconducting energy gaps \Delta_i(k) should appear on the
different electronic bands i. Here we introduce intra-band Bogoliubov
quasiparticle scattering interference (QPI) techniques for determination of
\Delta_i(k) in such materials, focusing on LiFeAs. We identify the three
hole-like bands assigned previously as \gamma, \alpha_2 and \alpha_1, and we
determine the anisotropy, magnitude and relative orientations of their
\Delta_i(k). These measurements will advance quantitative theoretical analysis
of the mechanism of Cooper pairing in iron-based superconductivity
Multi-Atom Quasiparticle Scattering Interference for Superconductor Energy-Gap Symmetry Determination
Complete theoretical understanding of the most complex superconductors
requires a detailed knowledge of the symmetry of the superconducting energy-gap
, for all momenta on the Fermi surface
of every band . While there are a variety of techniques for determining
, no general method existed to measure the signed
values of . Recently, however, a new technique based
on phase-resolved visualization of superconducting quasiparticle interference
(QPI) patterns centered on a single non-magnetic impurity atom, was introduced.
In principle, energy-resolved and phase-resolved Fourier analysis of these
images identifies wavevectors connecting all k-space regions where
has the same or opposite sign. But use of a single
isolated impurity atom, from whose precise location the spatial phase of the
scattering interference pattern must be measured is technically difficult. Here
we introduce a generalization of this approach for use with multiple impurity
atoms, and demonstrate its validity by comparing the
it generates to the determined from single-atom
scattering in FeSe where energy-gap symmetry is established. Finally,
to exemplify utility, we use the multi-atom technique on LiFeAs and find
scattering interference between the hole-like and electron-like pockets as
predicted for of opposite sign
Recurrent delirium over 12 months predicts dementia: results of the Delirium and Cognitive Impact in Dementia (DECIDE) study
Background: Delirium is common, distressing and associated with poor outcomes. Previous studies investigating the impact
of delirium on cognitive outcomes have been limited by incomplete ascertainment of baseline cognition or lack of prospective
delirium assessments. This study quantified the association between delirium and cognitive function over time by prospectively
ascertaining delirium in a cohort aged ≥ 65 years in whom baseline cognition had previously been established.
Methods: For 12 months, we assessed participants from the Cognitive Function and Ageing Study II-Newcastle for delirium
daily during hospital admissions. At 1-year, we assessed cognitive decline and dementia in those with and without delirium.
We evaluated the effect of delirium (including its duration and number of episodes) on cognitive function over time,
independently of baseline cognition and illness severity.
Results: Eighty two of 205 participants recruited developed delirium in hospital (40%). One-year outcome data were available
for 173 participants: 18 had a new dementia diagnosis, 38 had died. Delirium was associated with cognitive decline (−1.8
Mini-Mental State Examination points [95% CI –3.5 to –0.2]) and an increased risk of new dementia diagnosis at follow
up (OR 8.8 [95% CI 1.9–41.4]). More than one episode and more days with delirium (>5 days) were associated with worse
cognitive outcomes.
Conclusions: Delirium increases risk of future cognitive decline and dementia, independent of illness severity and baseline
cognition, with more episodes associated with worse cognitive outcomes. Given that delirium has been shown to be
preventable in some cases, we propose that delirium is a potentially modifiable risk factor for dementi
One health research in Northern Tanzania – challenges and progress
East Africa has one of the world’s fastest growing human populations—many of whom are dependent on livestock—as
well as some of the world’s largest wildlife populations. Humans, livestock, and wildlife often interact closely, intimately
linking human, animal, and environmental health. The concept of One Health captures this interconnectedness, including
the social structures and beliefs driving interactions between species and their environments. East African policymakers
and researchers are recognising and encouraging One Health research, with both groups increasingly playing a leading
role in this subject area. One Health research requires interaction between scientists from different disciplines, such as the
biological and social sciences and human and veterinary medicine. Different disciplines draw on norms, methodologies,
and terminologies that have evolved within their respective institutions and that may be distinct from or in conflict with one
another. These differences impact interdisciplinary research, both around theoretical and methodological approaches and
during project operationalisation. We present experiential knowledge gained from numerous ongoing projects in northern
Tanzania, including those dealing with bacterial zoonoses associated with febrile illness, foodborne disease, and anthrax.
We use the examples to illustrate differences between and within social and biological sciences and between industrialised
and traditional societies, for example, with regard to consenting procedures or the ethical treatment of animals. We
describe challenges encountered in ethical approval processes, consenting procedures, and field and laboratory logistics
and offer suggestions for improvement. While considerable investment of time in sensitisation, communication, and collaboration
is needed to overcome interdisciplinary challenges inherent in One Health research, this can yield great
rewards in paving the way for successful implementation of One Health projects. Furthermore, continued investment in
African institutions and scientists will strengthen the role of East Africa as a world leader in One Health research
Genetic and environmental pathways to complex diseases
<p>Abstract</p> <p>Background</p> <p>Pathogenesis of complex diseases involves the integration of genetic and environmental factors over time, making it particularly difficult to tease apart relationships between phenotype, genotype, and environmental factors using traditional experimental approaches.</p> <p>Results</p> <p>Using gene-centered databases, we have developed a network of complex diseases and environmental factors through the identification of key molecular pathways associated with both genetic and environmental contributions. Comparison with known chemical disease relationships and analysis of transcriptional regulation from gene expression datasets for several environmental factors and phenotypes clustered in a metabolic syndrome and neuropsychiatric subnetwork supports our network hypotheses. This analysis identifies natural and synthetic retinoids, antipsychotic medications, Omega 3 fatty acids, and pyrethroid pesticides as potential environmental modulators of metabolic syndrome phenotypes through PPAR and adipocytokine signaling and organophosphate pesticides as potential environmental modulators of neuropsychiatric phenotypes.</p> <p>Conclusion</p> <p>Identification of key regulatory pathways that integrate genetic and environmental modulators define disease associated targets that will allow for efficient screening of large numbers of environmental factors, screening that could set priorities for further research and guide public health decisions.</p
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