879 research outputs found
Impedance of a sphere oscillating in an elastic medium with and without slip
The dynamic impedance of a sphere oscillating in an elastic medium is
considered. Oestreicher's formula for the impedance of a sphere bonded to the
surrounding medium can be expressed simply in terms of three lumped impedances
associated with the displaced mass and the longitudinal and transverse waves.
If the surface of the sphere slips while the normal velocity remains
continuous, the impedance formula is modified by adjusting the definition of
the transverse impedance to include the interfacial impedance.Comment: 10 pages, 2 figure
Analyzing the heterogeneity of rule-based EHR phenotyping algorithms in CALIBER and the UK Biobank
Electronic Health Records (EHR) are data
generated during routine interactions across
healthcare settings and contain rich, longitudinal
information on diagnoses, symptoms, medications,
investigations and tests. A primary use-case for
EHR is the creation of phenotyping algorithms
used to identify disease status, onset and
progression or extraction of information on risk
factors or biomarkers. Phenotyping however is
challenging since EHR are collected for different
purposes, have variable data quality and often
require significant harmonization. While
considerable effort goes into the phenotyping
process, no consistent methodology for
representing algorithms exists in the UK. Creating
a national repository of curated algorithms can
potentially enable algorithm dissemination and
reuse by the wider community. A critical first step
is the creation of a robust minimum information
standard for phenotyping algorithm components
(metadata, implementation logic, validation
evidence) which involves identifying and
reviewing the complexity and heterogeneity of
current UK EHR algorithms. In this study, we
analyzed all available EHR phenotyping algorithms
(n=70) from two large-scale contemporary EHR
resources in the UK (CALIBER and UK Biobank).
We documented EHR sources, controlled clinical
terminologies, evidence of algorithm validation,
representation and implementation logic patterns.
Understanding the heterogeneity of UK EHR
algorithms and identifying common implementation patterns will facilitate the design of
a minimum information standard for representing
and curating algorithms nationally and
internationally
3D media stabilizes membrane and prolongs lifespan of defolliculated Xenopus laevis oocytes
Xenopus laevis oocytes are commonly used in many fundamental biological studies. One of the major limitations of X. laevis oocytes is their short storage lifespan with most defolliculated oocytes physically deteriorating in 10 days or less. Herein, we identified a 3D Cultrex-based storage media that incorporates extracellular membrane-based hydrogels to maintain oocyte integrity. Under these treatments, the lifespan of the oocytes increased to more than 20 days compared to standard conditions. The treatment preserved the oocytes membrane integrity and did not interfere with mRNA- or cDNA-derived protein expression
Does Apolipoprotein E Genotype Influence the Risk of Ischemic Stroke, Intracerebral Hemorrhage, or Subarachnoid Hemorrhage?: Systematic Review and Meta-Analyses of 31 Studies Among 5961 Cases and 17 965 Controls
BACKGROUND AND PURPOSE: Apolipoprotein E genotype (APOE) is associated with cholesterol metabolism, ischemic heart disease, and cerebral amyloid angiopathy, and so may affect risk of both ischemic and hemorrhagic stroke. METHODS: We comprehensively sought and identified studies of the association of apoE with ischemic stroke (IS), intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). We did meta-analyses to assess the evidence for an association between APOE and the various pathological types and subtypes of stroke, and assessed the effects of several methodological criteria. RESULTS: We analyzed data from 31 eligible studies (26 IS, 8 ICH, and 3 SAH) in 5961 cases and 17 965 controls. ∊4 allele-containing (∊4+) genotypes were significantly associated with IS (odds ratio [OR], 1.11; 95% CI, 1.01 to 1.22) and SAH (OR, 1.42; 95% CI, 1.01 to 1.99) and nonsignificantly with ICH (OR, 1.16; 95% CI, 0.93 to 1.44), whereas ∊2+ genotypes were associated with ICH (OR, 1.32; 95% CI, 1.01 to 1.74). Associations appeared stronger with ∊4+ genotypes for large artery compared with other IS subtypes and for Asian compared with white populations, and with ∊2+ genotypes for lobar compared with deep hemorrhages. However, we found no association between ∊4+ genotypes and IS when we analyzed only larger studies (>200 cases; OR, 0.99; 95% CI, 0.88 to 1.11) or studies without control selection bias (OR, 0.99; 95% CI, 0.85 to 1.17). CONCLUSIONS: Publication and selection biases make existing studies of APOE and stroke unreliable. Further, very large, methodologically rigorous studies are needed
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