363 research outputs found
Traumatic spinal cord injury caused by suspected hyperflexion of the atlantoaxial joint in a 10-year-old cat
Case summary:
A 10-year-old cat presented 5 days after a traumatic event with acute recumbency followed by some clinical improvement. The neuroanatomical localisation was the C1–C5 spinal cord segments. Initial survey radiographs, including lateral flexed views, showed no convincing abnormalities. Magnetic resonance imaging (MRI) revealed a marked focal intramedullary lesion at the level of the dens and suspected oedema extending over C2–C3 vertebrae, suggesting early syrinx formation. The cat made an initial excellent recovery on restricted exercise without medical treatment. The MRI changes largely resolved on follow-up MRI 4 weeks later yet recurred following a relapse 4 months later. At this stage, a post-traumatic syrinx had developed. Moreover, the suspected atlantoaxial instability was finally diagnosed on radiography with fully flexed lateral views. A hyperflexion injury causing tearing of the atlantoaxial ligaments was considered most likely given the lack of malformations or fractures. The cat made a full recovery on conservative management.
Relevance and novel information:
This is the first report of sequential MRI findings in a cat with atlantoaxial instability. Moreover, post-traumatic syringomyelia formation following atlantoaxial injury has not been reported. Sequential MRI aids in the diagnosis of hyperflexion injury if survey radiographs fail to identify atlantoaxial instability
The Learning Partnership Documentation: Final Report Summary
Summarizes MacArthur's initiative to support urban school reform through partnerships with districts and to refine a theory of systemic educational change. Outlines the conceptual framework, the role of documentation, challenges, and lessons learned
Molecular Modification of CNT Junctions
Carbon nanotube networks (CNNs) are increasingly finding applications as thin film transistors (TFTs), integrated circuits, and display drivers on flexible, transparent substrates. This is attributed to the higher carrier mobility of CNNs as compared to amorphous silicon and organic TFTs [1,2]. However, high electrical [3-5] and thermal [6,7] resistances at individual nanotube junctions (NJs) limit the performance of CNN devices. The resistances of the junctions are no less than an order of magnitude higher than those of individual carbon nanotubes (CNTs). This causes high power dissipation at the NJs. In the end this causes degradation of the overall device performance and reliability [3,4]. Previous studies have shown how molecular modification of CNT junctions can reduce the sheet resistance of conducting and transparent CNN electrodes. [refs to Vikar and Bao]. However, to our knowledge, the effects of molecular modification of CNT junctions on device performance remain unreported.
In this study, we present a novel method to improve CNN TFT performance, through the application of 0-dimensional (0D) molecules, e.g. C60 fullerenes and CdSe quantum dots, onto the surface of the CNN device. These materials can be applied through spin-coating, dip-coating, or spray coating. We find the absorbance spectra of the 0D materials correlate with their HOMO-LUMO gap and concentration of these molecules in solution. Our preliminary data also suggest preferential attachment of these nanoparticles to NJs, eliminating the need for lithography to selectively deposit 0D materials at NJs. Our results suggests these molecules may act as a nanosolder or nanoglue at the NJs, modifying their electrical and thermal resistances for improved device performance.
[1] D. Sun, et al., Nat. Nanotechnol. 6, 156 (2011); [2] Q. Cao, et al., Nature 454, 495 (2008); [3] P. Nirmalraj, et al., Nano Lett. 9, 3890 (2009); [4] M. Stadermann, et al., Phys. Rev. B: Condens. Matter Mater. Phys. 69, 201402 (2004); [5] A. Kyrylyuk, et al., Nat. Nanotechnol. 6, 364 (2011); [6] R. Prasher, et al., Phys. Rev. Lett. 102, 105901 (2009); [7] J. Yang, et al., Appl. Phys. Lett. 96, 023109 (2010)
Intraoperative detection of blood vessels with an imaging needle during neurosurgery in humans
Intracranial hemorrhage can be a devastating complication associated with needle biopsies of the brain. Hemorrhage can occur to vessels located adjacent to the biopsy needle as tissue is aspirated into the needle and removed. No intraoperative technology exists to reliably identify blood vessels that are at risk of damage. To address this problem, we developed an “imaging needle” that can visualize nearby blood vessels in real time. The imaging needle contains a miniaturized optical coherence tomography probe that allows differentiation of blood flow and tissue. In 11 patients, we were able to intraoperatively detect blood vessels (diameter, \u3e500 μm) with a sensitivity of 91.2% and a specificity of 97.7%. This is the first reported use of an optical coherence tomography needle probe in human brain in vivo. These results suggest that imaging needles may serve as a valuable tool in a range of neurosurgical needle interventions
Patient engagement with radiation therapists: Patient perspectives, challenges, and opportunities. A Systematic review
A Hierarchical Bayesian Approach to Neutron Spectrum Unfolding with Organic Scintillators
We propose a hierarchical Bayesian model and state-of-art Monte Carlo
sampling method to solve the unfolding problem, i.e., to estimate the spectrum
of an unknown neutron source from the data detected by an organic scintillator.
Inferring neutron spectra is important for several applications, including
nonproliferation and nuclear security, as it allows the discrimination of
fission sources in special nuclear material (SNM) from other types of neutron
sources based on the differences of the emitted neutron spectra. Organic
scintillators interact with neutrons mostly via elastic scattering on hydrogen
nuclei and therefore partially retain neutron energy information. Consequently,
the neutron spectrum can be derived through deconvolution of the measured light
output spectrum and the response functions of the scintillator to monoenergetic
neutrons. The proposed approach is compared to three existing methods using
simulated data to enable controlled benchmarks. We consider three sets of
detector responses. One set corresponds to a 2.5 MeV monoenergetic neutron
source and two sets are associated with (energy-wise) continuous neutron
sources (Cf and AmBe). Our results show that the proposed
method has similar or better unfolding performance compared to other iterative
or Tikhonov regularization-based approaches in terms of accuracy and robustness
against limited detection events, while requiring less user supervision. The
proposed method also provides a posteriori confidence measures, which offers
additional information regarding the uncertainty of the measurements and the
extracted information.Comment: 10 page
Adverse childhood experiences, epigenetics and telomere length variation in childhood and beyond: a systematic review of the literature
A systematic review following PRISMA guidelines was conducted to answer the question: What epigenetic, telomeric and associated biological changes are associated with exposure to adverse childhood experiences (ACEs) in the under 12s? Using PRISMA guidelines, appropriate databases were searched. 190 papers were returned with 38 articles fully reviewed. Articles were each independently quality rated by two authors using the Crowe Critical Appraisal Tool and data were extracted. Of the 38 articles, 23 were rated as very high quality. Most study participants were adults (n = 7769) with n = 727 child participants. Only seven of the very/high-quality studies were prospective and involved children. Methylation was the most studied method of epigenetic modification. There is some evidence supporting epigenetic modification of certain markers in participants exposed to ACEs measured in adulthood. Research is lacking on non-coding aspects of the epigenome and on coding aspects other than DNA methylation. There is some evidence of a more powerful effect on telomere length if physical neglect was involved. Much further work is required to model biological and psychological effects of epigenetic changes during childhood using prospective study designs. The effect of ACEs on the cellular ageing process during childhood is inadequately investigated and relies solely on measure of telomere length. Future research suggestions are proposed
Bayesian Activity Estimation and Uncertainty Quantification of Spent Nuclear Fuel Using Passive Gamma Emission Tomography
In this paper, we address the problem of activity estimation in passive gamma emission tomography (PGET) of spent nuclear fuel. Two different noise models are considered and compared, namely, the isotropic Gaussian and the Poisson noise models. The problem is formulated within a Bayesian framework as a linear inverse problem and prior distributions are assigned to the unknown model parameters. In particular, a Bernoulli-truncated Gaussian prior model is considered to promote sparse pin configurations. A Markov chain Monte Carlo (MCMC) method, based on a split and augmented Gibbs sampler, is then used to sample the posterior distribution of the unknown parameters. The proposed algorithm is first validated by simulations conducted using synthetic data, generated using the nominal models. We then consider more realistic data simulated using a bespoke simulator, whose forward model is non-linear and not available analytically. In that case, the linear models used are mis-specified and we analyse their robustness for activity estimation. The results demonstrate superior performance of the proposed approach in estimating the pin activities in different assembly patterns, in addition to being able to quantify their uncertainty measures, in comparison with existing methods
Optimized media and workflow for the expansion of human pluripotent stem cells as aggregates in suspension
3D suspension culture enables the efficient and cost-effective scale-up of human pluripotent stem cell (hPSCs) manufacturing. However, media optimized for 2D adherent cultures can lead to low volumetric productivity and inefficient workflow. To overcome these limitations we developed mTeSRTM3D, a defined medium based on mTeSRTM1, and novel protocols for fed-batch culture of hPSC aggregates. Human embryonic stem cell (hESC) lines (H1 or H9) or human induced pluripotent stem cell (hiPSC) lines (WLS-1C or STiPS-M001) that were previously maintained in 2D mTeSRTM1 culture were seeded into multiple suspension culture vessels containing mTeSRTM3D Seed Medium plus 10 μM Y-27632 ROCK inhibitor. 3D cultures were maintained using either daily 50% mTeSRTM1 medium exchanges (control) or using a fed-batch protocol whereby the culture medium was supplemented daily with mTeSRTM3D Feed Medium. After 3 or 4 days in suspension culture, aggregates were harvested, dissociated into small clumps with Gentle Cell Dissociation Reagent (GCDR) or single cell suspensions enzymatically, and re-seeded in mTeSRTM3D Seed Medium plus 10 μM Y-27632. Passaging and feeding cycles were repeated for at least 5 passages. 3D cultures were assessed for growth, viability, hPSC marker expression, in vitro differentiation potential, and karyotype. In addition, media was analyzed for molar glucose to lactate yield to characterize metabolism. By day 4, aggregates cultured in mTeSRTM3D typically grew to a mean diameter of 350 μm, with a 5-fold increase in cell number. Using mTeSRTM3D up to 109 cells can be produced from a single plate within 2-3 weeks representing a greater than 500-fold expansion. hPSC cultures maintained in mTeSRTM3D differentiated into all 3 germ layers with high efficiency. The average volumetric productivities were 0.7, 3.1 and 6.9 (x105) viable cells / mL in 2D, daily 50% media exchange, and mTeSRTM3D cultures, respectively. Using the GCDR clump passaging protocol, mTeSRTM3D cultured hPSCs retained normal karyotypes. Culture performance was evaluated in shaker bottles, spinner flasks and bioreactors. Performance in each culture system was comparable confirming straightforward scale-up and wide applicability. Typical growth rates were on the order of 1.5-fold expansion per day. Metabolic activity as assessed by the moles lactate produced to glucose consumed was 1.7, consistent with a primarily glycolytic metabolism. Image analysis was performed to estimate aggregate size during growth. Adaptation times for cells moving from 2D to 3D aggregate culture varied with different cell lines; typically one passage in 3D was required before consistent expansion passage over passage was obtained. Additionally, protocols were developed for use on a Hamilton® robotic platform for reproducible, matrix-free, high-throughput hPSC suspension culture at a small scale. mTeSRTM3D enables efficient scale-up and scale-down of hPSC cultures with greatly simplified workflow
A search for dispersed radio bursts in archival Parkes Multibeam Pulsar Survey data
A number of different classes of potentially extra-terrestrial bursts of
radio emission have been observed in surveys with the Parkes 64m radio
telescope, including "Rotating Radio Transients", the "Lorimer burst" and
"perytons". Rotating Radio Transients are radio pulsars which are best
detectable in single-pulse searches. The Lorimer burst is a highly dispersed
isolated radio burst with properties suggestive of extragalactic origin.
Perytons share the frequency-swept nature of the Rotating Radio Transients and
Lorimer burst, but unlike these events appear in all thirteen beams of the
Parkes Multibeam receiver and are probably a form of peculiar radio frequency
interference. In order to constrain these and other radio source populations
further, we searched the archival Parkes Multibeam Pulsar Survey data for
events similar to any of these. We did not find any new Rotating Radio
Transients or bursts like the Lorimer burst. We did, however, discover four
peryton-like events. Similar to the perytons, these four bursts are highly
dispersed, detected in all thirteen beams of the Parkes multibeam receiver, and
have pulse widths between 20--30 ms. Unlike perytons, these bursts are not
associated with atmospheric events like rain or lightning. These facts may
indicate that lightning was not responsible for the peryton phenomenon.
Moreover, the lack of highly dispersed celestial signals is the evidence that
the Lorimer burst is unlikely to belong to a cosmological source population.Comment: Accepted for publication in MNRAS; 7 pages, 3 figures, 1 tabl
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